Rotating black holes in dilatonic Einstein-Gauss-Bonnet theory.
Kleihaus, Burkhard; Kunz, Jutta; Radu, Eugen
2011-04-15
We construct generalizations of the Kerr black holes by including higher-curvature corrections in the form of the Gauss-Bonnet density coupled to the dilaton. We show that the domain of existence of these Einstein-Gauss-Bonnet-dilaton (EGBD) black holes is bounded by the Kerr black holes, the critical EGBD black holes, and the singular extremal EGBD solutions. The angular momentum of the EGBD black holes can exceed the Kerr bound. The EGBD black holes satisfy a generalized Smarr relation. We also compare their innermost stable circular orbits with those of the Kerr black holes and show the existence of differences which might be observable in astrophysical systems.
Electrically charged dilatonic black rings
International Nuclear Information System (INIS)
Kunduri, Hari K.; Lucietti, James
2005-01-01
In this Letter we present (electrically) charged dilatonic black ring solutions of the Einstein-Maxwell-dilaton theory in five dimensions and we consider their physical properties. These solutions are static and as in the neutral case possess a conical singularity. We show how one may remove the conical singularity by application of a Harrison transformation, which physically corresponds to supporting the charged ring with an electric field. Finally, we discuss the slowly rotating case for arbitrary dilaton coupling
Rotating dilaton black holes with hair
International Nuclear Information System (INIS)
Kleihaus, Burkhard; Kunz, Jutta; Navarro-Lerida, Francisco
2004-01-01
We consider stationary rotating black holes in SU(2) Einstein-Yang-Mills theory, coupled to a dilaton. The black holes possess nontrivial non-Abelian electric and magnetic fields outside their regular event horizon. While generic solutions carry no non-Abelian magnetic charge, but non-Abelian electric charge, the presence of the dilaton field allows also for rotating solutions with no non-Abelian charge at all. As a consequence, these special solutions do not exhibit the generic asymptotic noninteger power falloff of the non-Abelian gauge field functions. The rotating black hole solutions form sequences, characterized by the winding number n and the node number k of their gauge field functions, tending to embedded Abelian black holes. The stationary non-Abelian black hole solutions satisfy a mass formula, similar to the Smarr formula, where the dilaton charge enters instead of the magnetic charge. Introducing a topological charge, we conjecture that black hole solutions in SU(2) Einstein-Yang-Mills-dilaton theory are uniquely characterized by their mass, their angular momentum, their dilaton charge, their non-Abelian electric charge, and their topological charge
Dilaton field released under collision of dilatonic black holes with Gauss-Bonnet term
Energy Technology Data Exchange (ETDEWEB)
Gwak, Bogeun [Sejong University, Department of Physics and Astronomy, Seoul (Korea, Republic of); Ro, Daeho [POSTECH, Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk (Korea, Republic of)
2017-08-15
We investigate the upper limit of the gravitational radiation released upon the collision of two dilatonic black holes by analyzing the Gauss-Bonnet term. Dilatonic black holes have a dilaton hair coupled with this term. Using the laws of thermodynamics, the upper limit of the radiation is obtained, which reflected the effects of the dilaton hair. The amount of radiation released is greater than that emitted by a Schwarzschild black hole due to the contribution from the dilaton hair. In the collision, most of the dilaton hair can be released through radiation, where the energy radiated by the dilaton hair is maximized when the horizon of one black hole is minimized for a fixed second black hole. (orig.)
Fermionic greybody factors in dilaton black holes
International Nuclear Information System (INIS)
Abedi, Jahed; Arfaei, Hessamaddin
2014-01-01
In this paper the question of the emission of fermions in the process of dilaton black hole evolution and its characteristics for different dilaton coupling constants α are studied. The main quantity of interest, the greybody factors, are calculated both numerically and in analytical approximation. The dependence of the rates of evaporation and behaviour on the dilaton coupling constant is analysed. Having calculated the greybody factors, we are able to address the question of the final fate of the dilaton black hole. For that we also need to perform dynamical treatment of the solution by considering the backreaction, which will show a crucial effect on the final result. We find a transition line in the (Q/M,α) plane that separates the two regimes for the fate of the black hole, decay regime and extremal regime. In the decay regime the black hole completely evaporates, while in the extremal regime the black hole approaches the extremal limit by radiation and becomes stable. (paper)
Pair creation of dilaton black holes in extended inflation
International Nuclear Information System (INIS)
Bousso, R.
1997-01-01
Dilatonic charged Nariai instantons mediate the nucleation of black hole pairs during extended chaotic inflation. Depending on the dilaton and inflaton fields, the black holes are described by one of two approximations in the Lorentzian regime. For each case we find Euclidean solutions that satisfy the no boundary proposal. The complex initial values of the dilaton and inflaton are determined, and the pair creation rate is calculated from the Euclidean action. Similar to standard inflation, black holes are abundantly produced near the Planck boundary, but highly suppressed later on. An unusual feature we find is that the earlier in inflation the dilatonic black holes are created, the more highly charged they can be. copyright 1997 The American Physical Society
Rotating Dilaton Black Strings Coupled to Exponential Nonlinear Electrodynamics
Directory of Open Access Journals (Sweden)
Ahmad Sheykhi
2014-01-01
Full Text Available We construct a new class of charged rotating black string solutions coupled to dilaton and exponential nonlinear electrodynamic fields with cylindrical or toroidal horizons in the presence of a Liouville-type potential for the dilaton field. Due to the presence of the dilaton field, the asymptotic behaviors of these solutions are neither flat nor (AdS. We analyze the physical properties of the solutions in detail. We compute the conserved and thermodynamic quantities of the solutions and verify the first law of thermodynamics on the black string horizon. When the nonlinear parameter β2 goes to infinity, our results reduce to those of black string solutions in Einstein-Maxwell-dilaton gravity.
Black hole dynamics in Einstein-Maxwell-dilaton theory
Hirschmann, Eric W.; Lehner, Luis; Liebling, Steven L.; Palenzuela, Carlos
2018-03-01
We consider the properties and dynamics of black holes within a family of alternative theories of gravity, namely Einstein-Maxwell-dilaton theory. We analyze the dynamical evolution of individual black holes as well as the merger of binary black hole systems. We do this for a wide range of parameter values for the family of Einstein-Maxwell-dilaton theories, investigating, in the process, the stability of these black holes. We examine radiative degrees of freedom, explore the impact of the scalar field on the dynamics of merger, and compare with other scalar-tensor theories. We argue that the dilaton can largely be discounted in understanding merging binary systems and that the end states essentially interpolate between charged and uncharged, rotating black holes. For the relatively small charge values considered here, we conclude that these black hole systems will be difficult to distinguish from their analogs within General Relativity.
Thermal fluctuations of dilaton black holes in gravity's rainbow
Dehghani, M.
2018-06-01
In this work, thermodynamics and phase transition of some new dilaton black hole solutions have been explored in the presence of the rainbow functions. By introducing an energy dependent space time, the dilaton potential has been obtained as the linear combination of two Liouville-type potentials and three new classes of black hole solutions have been constructed. The conserved and thermodynamic quantities of the new dilaton black holes have been calculated in the energy dependent space times. It has been shown that, even if some of the thermodynamic quantities are affected by the rainbow functions, the thermodynamical first law still remains valid. Also, the impacts of rainbow functions on the stability or phase transition of the new black hole solutions have been investigated. Finally, the quantum gravitational effects on the thermodynamics and phase transition of the solutions have been studied through consideration of the thermal fluctuations.
Entropy of charged dilaton-axion black hole
International Nuclear Information System (INIS)
Ghosh, Tanwi; SenGupta, Soumitra
2008-01-01
Using the brick wall method, the entropy of the charged dilaton-axion black hole is determined for both asymptotically flat and nonflat cases. The entropy turns out to be proportional to the horizon area of the black hole confirming the Bekenstein-Hawking area-entropy formula for black holes. The leading order logarithmic corrections to the entropy are also derived for such black holes.
Thermodynamic Relations for Kiselev and Dilaton Black Hole
International Nuclear Information System (INIS)
Jamil, Mubasher; Pradhan, Parthapratim; Majeed, Bushra
2015-01-01
We investigate the thermodynamics and phase transition for Kiselev black hole and dilaton black hole. Specifically we consider Reissner-Nordström black hole surrounded by radiation and dust and Schwarzschild black hole surrounded by quintessence, as special cases of Kiselev solution. We have calculated the products relating the surface gravities, surface temperatures, Komar energies, areas, entropies, horizon radii, and the irreducible masses at the Cauchy and the event horizons. It is observed that the product of surface gravities, product of surface temperature, and product of Komar energies at the horizons are not universal quantities for the Kiselev solutions while products of areas and entropies at both the horizons are independent of mass of the above-mentioned black holes (except for Schwarzschild black hole surrounded by quintessence). For charged dilaton black hole, all the products vanish. The first law of thermodynamics is also verified for Kiselev solutions. Heat capacities are calculated and phase transitions are observed, under certain conditions
Higher-n triangular dilatonic black holes
Zadora, Anton; Gal'tsov, Dmitri V.; Chen, Chiang-Mei
2018-04-01
Dilaton gravity with the form fields is known to possess dyon solutions with two horizons for the discrete "triangular" values of the dilaton coupling constant a =√{ n (n + 1) / 2 }. This sequence first obtained numerically and then explained analytically as consequence of the regularity of the dilaton, should have some higher-dimensional and/or group theoretical origin. Meanwhile, this origin was explained earlier only for n = 1 , 2 in which cases the solutions were known analytically. We extend this explanation to n = 3 , 5 presenting analytical triangular solutions for the theory with different dilaton couplings a , b in electric and magnetic sectors in which case the quantization condition reads ab = n (n + 1) / 2. The solutions are derived via the Toda chains for B2 and G2 Lie algebras. They are found in the closed form in general D space-time dimensions. Solutions satisfy the entropy product rules indicating on the microscopic origin of their entropy and have negative binding energy in the extremal case.
Heat engines for dilatonic Born-Infeld black holes
Energy Technology Data Exchange (ETDEWEB)
Bhamidipati, Chandrasekhar; Yerra, Pavan Kumar [Indian Institute of Technology Bhubaneswar, School of Basic Sciences, Bhubaneswar (India)
2017-08-15
In the context of dilaton coupled Einstein gravity with a negative cosmological constant and a Born-Infeld field, we study heat engines where a charged black hole is the working substance. Using the existence of a notion of thermodynamic mass and volume (which depend on the dilaton coupling), the mechanical work takes place via the pdV terms present in the first law of extended gravitational thermodynamics. The efficiency is analyzed as a function of dilaton and Born-Infeld couplings, and the results are compared with analogous computations in the related conformal solutions in the Brans-Dicke-Born-Infeld theory and black holes in anti-de Sitter space-time. (orig.)
Thermodynamics of novel charged dilatonic BTZ black holes
Dehghani, M.
2017-10-01
In this paper, the three-dimensional Einstein-Maxwell theory in the presence of a dilatonic scalar field has been studied. It has been shown that the dilatonic potential must be considered as the linear combination of two Liouville-type potentials. Two new classes of charged dilatonic BTZ black holes, as the exact solutions to the coupled scalar, vector and tensor field equations, have been obtained and their properties have been studied. The conserved charge and mass of the new black holes have been calculated, making use of the Gauss's law and Abbott-Deser proposal, respectively. Through comparison of the thermodynamical extensive quantities (i.e. temperature and entropy) obtained from both, the geometrical and the thermodynamical methods, the validity of the first law of black hole thermodynamics has been confirmed for both of the new black holes we just obtained. A black hole thermal stability or phase transition analysis has been performed, making use of the canonical ensemble method. Regarding the black hole heat capacity, it has been found that for either of the new black hole solutions there are some specific ranges in such a way that the black holes with the horizon radius in these ranges are locally stable. The points of type one and type two phase transitions have been determined. The black holes, with the horizon radius equal to the transition points are unstable. They undergo type one or type two phase transitions to be stabilized.
Six-dimensional Yang black holes in dilaton gravity
International Nuclear Information System (INIS)
Abbott, Michael C.; Lowe, David A.
2008-01-01
We study the six-dimensional dilaton gravity Yang black holes of Bergshoeff, Gibbons and Townsend, which carry (1,-1) charge in SU(2)xSU(2) gauge group. We find what values of the asymptotic parameters (mass and scalar charge) lead to a regular horizon, and show that there are no regular solutions with an extremal horizon
Charged dilatonic black holes in gravity's rainbow
Energy Technology Data Exchange (ETDEWEB)
Hendi, S.H. [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); Faizal, Mir [University of Waterloo, Department of Physics and Astronomy, Waterloo, ON (Canada); Panah, B.E. [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of); Panahiyan, S. [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of); Shahid Beheshti University, Physics Department, Tehran (Iran, Islamic Republic of)
2016-05-15
In this paper, we present charged dilatonic black holes in gravity's rainbow. We study the geometric and thermodynamic properties of black hole solutions. We also investigate the effects of rainbow functions on different thermodynamic quantities for these charged black holes in dilatonic gravity's rainbow. Then we demonstrate that the first law of thermodynamics is valid for these solutions. After that, we investigate thermal stability of the solutions using the canonical ensemble and analyze the effects of different rainbow functions on the thermal stability. In addition, we present some arguments regarding the bound and phase transition points in context of geometrical thermodynamics. We also study the phase transition in extended phase space in which the cosmological constant is treated as the thermodynamic pressure. Finally, we use another approach to calculate and demonstrate that the obtained critical points in extended phase space represent a second order phase transition for these black holes. (orig.)
Thermodynamics of charged dilatonic BTZ black holes in rainbow gravity
Dehghani, M.
2018-02-01
In this paper, the charged three-dimensional Einstein's theory coupled to a dilatonic field has been considered in the rainbow gravity. The dilatonic potential has been written as the linear combination of two Liouville-type potentials. Four new classes of charged dilatonic rainbow black hole solutions, as the exact solution to the coupled field equations of the energy dependent space time, have been obtained. Two of them are correspond to the Coulomb's electric field and the others are consequences of a modified Coulomb's law. Total charge and mass as well as the entropy, temperature and electric potential of the new charged black holes have been calculated in the presence of rainbow functions. Although the thermodynamic quantities are affected by the rainbow functions, it has been found that the first law of black hole thermodynamics is still valid for all of the new black hole solutions. At the final stage, making use of the canonical ensemble method and regarding the black hole heat capacity, the thermal stability or phase transition of the new rainbow black hole solutions have been analyzed.
Thermodynamics of charged dilatonic BTZ black holes in rainbow gravity
Directory of Open Access Journals (Sweden)
M. Dehghani
2018-02-01
Full Text Available In this paper, the charged three-dimensional Einstein's theory coupled to a dilatonic field has been considered in the rainbow gravity. The dilatonic potential has been written as the linear combination of two Liouville-type potentials. Four new classes of charged dilatonic rainbow black hole solutions, as the exact solution to the coupled field equations of the energy dependent space time, have been obtained. Two of them are correspond to the Coulomb's electric field and the others are consequences of a modified Coulomb's law. Total charge and mass as well as the entropy, temperature and electric potential of the new charged black holes have been calculated in the presence of rainbow functions. Although the thermodynamic quantities are affected by the rainbow functions, it has been found that the first law of black hole thermodynamics is still valid for all of the new black hole solutions. At the final stage, making use of the canonical ensemble method and regarding the black hole heat capacity, the thermal stability or phase transition of the new rainbow black hole solutions have been analyzed.
Topology, entropy, and Witten index of dilaton black holes
International Nuclear Information System (INIS)
Gibbons, G.W.; Kallosh, R.E.
1995-01-01
We have found that for extreme dilaton black holes an inner boundary must be introduced in addition to the outer boundary to give an integer value to the Euler number. The resulting manifolds have (if one identifies imaginary time) a topology S 1 xRxS 2 and Euler number χ=0 in contrast with the nonextreme case with χ=2. The entropy of extreme U(1) dilaton black holes is already known to be zero. We include a review of some recent ideas due to Hawking on the Reissner-Nordstroem case. By regarding all extreme black holes as having an inner boundary, we conclude that the entropy of all extreme black holes, including [U(1)] 2 black holes, vanishes. We discuss the relevance of this to the vanishing of quantum corrections and the idea that the functional integral for extreme holes gives a Witten index. We have studied also the topology of ''moduli space'' of multi-black-holes. The quantum mechanics on black hole moduli spaces is expected to be supersymmetric despite the fact that they are not hyper-Kaehler since the corresponding geometry has a torsion unlike the BPS monopole case. Finally, we describe the possibility of extreme black hole fission for states with an energy gap. The energy released, as a proportion of the initial rest mass, during the decay of an electromagnetic black hole is 300 times greater than that released by the fission of a 235 U nucleus
The information entropy of a static dilaton black hole
Institute of Scientific and Technical Information of China (English)
2008-01-01
In accordance with holographic principle, by calculating the statistical entropy of the quantum field just at the event horizon of the Garfinkle-Horowitz-Strominger dilaton black hole, the information entropy of the black hole was investigated and the Bekenstein-Hawking formula was obtained. The results show that black hole entropy is identical with the statistical entropy of the quantum field at the horizon. Using the generalized uncertainty relation, the divergence of the state density near the event horizon in usual quantum field theory was removed, and the cutoffs and the little mass approximation in the heat gas method of black hole entropy were avoided. Thus, the microstates of the massive scalar field just at the event horizon of the static dilaton black hole were studied directly and a description on holograph principle was presented. By using residue theorem, the integral difficulty in the calculation was overcome, and the information entropy and the Bekenstein-Hawking formula were obtained quantitatively. Compared with the black hole entropy from the loop quantum gravity, the consistency of methods and results of calculating black hole entropy in non-commutative quantum field theory and loop quantum gravity was investigated. By this, the gravity correction constant in the generalized uncertainty relation was suggested and the sense of holographic principle was discussed.
Dilatonic BTZ black holes with power-law field
International Nuclear Information System (INIS)
Hendi, S.H.; Eslam Panah, B.; Panahiyan, S.; Sheykhi, A.
2017-01-01
Motivated by low energy effective action of string theory and numerous applications of BTZ black holes, we will consider minimal coupling between dilaton and nonlinear electromagnetic fields in three dimensions. The main goal is studying thermodynamical structure of black holes in this set up. Temperature and heat capacity of these black holes are investigated and a picture regarding their phase transitions is given. In addition, the role and importance of studying the mass of black holes is highlighted. We will see how different parameters modify thermodynamical quantities, hence thermodynamical structure of these black holes. In addition, geometrical thermodynamics is used to investigate thermodynamical properties of these black holes. In this regard, the successful method is presented and the nature of interaction around bound and phase transition points is studied.
Dilatonic BTZ black holes with power-law field
Energy Technology Data Exchange (ETDEWEB)
Hendi, S.H., E-mail: hendi@shirazu.ac.ir [Physics Department and Biruni Observatory, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha P.O. Box 55134-441 (Iran, Islamic Republic of); Eslam Panah, B., E-mail: behzad.eslampanah@gmail.com [Physics Department and Biruni Observatory, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha P.O. Box 55134-441 (Iran, Islamic Republic of); Panahiyan, S., E-mail: sh.panahiyan@gmail.com [Physics Department and Biruni Observatory, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Physics Department, Shahid Beheshti University, Tehran 19839 (Iran, Islamic Republic of); Sheykhi, A., E-mail: asheykhi@shirazu.ac.ir [Physics Department and Biruni Observatory, College of Sciences, Shiraz University, Shiraz 71454 (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha P.O. Box 55134-441 (Iran, Islamic Republic of)
2017-04-10
Motivated by low energy effective action of string theory and numerous applications of BTZ black holes, we will consider minimal coupling between dilaton and nonlinear electromagnetic fields in three dimensions. The main goal is studying thermodynamical structure of black holes in this set up. Temperature and heat capacity of these black holes are investigated and a picture regarding their phase transitions is given. In addition, the role and importance of studying the mass of black holes is highlighted. We will see how different parameters modify thermodynamical quantities, hence thermodynamical structure of these black holes. In addition, geometrical thermodynamics is used to investigate thermodynamical properties of these black holes. In this regard, the successful method is presented and the nature of interaction around bound and phase transition points is studied.
Dilatonic BTZ black holes with power-law field
Hendi, S. H.; Eslam Panah, B.; Panahiyan, S.; Sheykhi, A.
2017-04-01
Motivated by low energy effective action of string theory and numerous applications of BTZ black holes, we will consider minimal coupling between dilaton and nonlinear electromagnetic fields in three dimensions. The main goal is studying thermodynamical structure of black holes in this set up. Temperature and heat capacity of these black holes are investigated and a picture regarding their phase transitions is given. In addition, the role and importance of studying the mass of black holes is highlighted. We will see how different parameters modify thermodynamical quantities, hence thermodynamical structure of these black holes. In addition, geometrical thermodynamics is used to investigate thermodynamical properties of these black holes. In this regard, the successful method is presented and the nature of interaction around bound and phase transition points is studied.
Timelike geodesics around a charged spherically symmetric dilaton black hole
Directory of Open Access Journals (Sweden)
Blaga C.
2015-01-01
Full Text Available In this paper we study the timelike geodesics around a spherically symmetric charged dilaton black hole. The trajectories around the black hole are classified using the effective potential of a free test particle. This qualitative approach enables us to determine the type of orbit described by test particle without solving the equations of motion, if the parameters of the black hole and the particle are known. The connections between these parameters and the type of orbit described by the particle are obtained. To visualize the orbits we solve numerically the equation of motion for different values of parameters envolved in our analysis. The effective potential of a free test particle looks different for a non-extremal and an extremal black hole, therefore we have examined separately these two types of black holes.
Brane cosmology with curvature corrections
International Nuclear Information System (INIS)
Kofinas, Georgios; Maartens, Roy; Papantonopoulos, Eleftherios
2003-01-01
We study the cosmology of the Randall-Sundrum brane-world where the Einstein-Hilbert action is modified by curvature correction terms: a four-dimensional scalar curvature from induced gravity on the brane, and a five-dimensional Gauss-Bonnet curvature term. The combined effect of these curvature corrections to the action removes the infinite-density big bang singularity, although the curvature can still diverge for some parameter values. A radiation brane undergoes accelerated expansion near the minimal scale factor, for a range of parameters. This acceleration is driven by the geometric effects, without an inflation field or negative pressures. At late times, conventional cosmology is recovered. (author)
Hawking radiation from dilatonic black holes via anomalies
International Nuclear Information System (INIS)
Jiang Qingquan; Cai Xu; Wu Shuangqing
2007-01-01
Recently, Hawking radiation from a Schwarzschild-type black hole via a gravitational anomaly at the horizon has been derived by Robinson and Wilczek. Their result shows that, in order to demand general coordinate covariance at the quantum level to hold in the effective theory, the flux of the energy-momentum tensor required to cancel the gravitational anomaly at the horizon of the black hole is exactly equal to that of (1+1)-dimensional blackbody radiation at the Hawking temperature. In this paper, we attempt to apply the analysis to derive Hawking radiation from the event horizons of static, spherically symmetric dilatonic black holes with arbitrary coupling constant α, and that from the rotating Kaluza-Klein (α=√(3)) as well as the Kerr-Sen (α=1) black holes via an anomalous point of view. Our results support Robinson and Wilczek's opinion. In addition, the properties of the obtained physical quantities near the extreme limit are qualitatively discussed
Hamiltonian thermodynamics of charged three-dimensional dilatonic black holes
International Nuclear Information System (INIS)
Dias, Goncalo A. S.; Lemos, Jose P. S.
2008-01-01
The action for a class of three-dimensional dilaton-gravity theories, with an electromagnetic Maxwell field and a cosmological constant, can be recast in a Brans-Dicke-Maxwell type action, with its free ω parameter. For a negative cosmological constant, these theories have static, electrically charged, and spherically symmetric black hole solutions. Those theories with well formulated asymptotics are studied through a Hamiltonian formalism, and their thermodynamical properties are found out. The theories studied are general relativity (ω→±∞), a dimensionally reduced cylindrical four-dimensional general relativity theory (ω=0), and a theory representing a class of theories (ω=-3), all with a Maxwell term. The Hamiltonian formalism is set up in three dimensions through foliations on the right region of the Carter-Penrose diagram, with the bifurcation 1-sphere as the left boundary, and anti-de Sitter infinity as the right boundary. The metric functions on the foliated hypersurfaces and the radial component of the vector potential one-form are the canonical coordinates. The Hamiltonian action is written, the Hamiltonian being a sum of constraints. One finds a new action which yields an unconstrained theory with two pairs of canonical coordinates (M,P M ;Q,P Q ), where M is the mass parameter, which for ω M is the conjugate momenta of M, Q is the charge parameter, and P Q is its conjugate momentum. The resulting Hamiltonian is a sum of boundary terms only. A quantization of the theory is performed. The Schroedinger evolution operator is constructed, the trace is taken, and the partition function of the grand canonical ensemble is obtained, where the chemical potential is the scalar electric field φ. Like the uncharged cases studied previously, the charged black hole entropies differ, in general, from the usual quarter of the horizon area due to the dilaton.
An alternative perspective to observe the critical phenomena of dilaton black holes
Energy Technology Data Exchange (ETDEWEB)
Mo, Jie-Xiong [Lingnan Normal University, Institute of Theoretical Physics, Zhanjiang, Guangdong (China)
2017-08-15
The critical phenomena of dilaton black holes are probed from a totally different perspective other than the P-v criticality and the q-U criticality discussed in former literature. We investigate not only the two point correlation function but also the entanglement entropy of dilaton black holes. For both the two point correlation function and the entanglement entropy we consider 4 x 2 x 2 = 16 cases due to different choices of parameters. The van der Waals-like behavior can be clearly witnessed from all the T -δL (T -δS) graphs for q < q{sub c}. Moreover, the effects of dilaton gravity and the spacetime dimensionality on the phase structure of dilaton black holes are disclosed. Furthermore, we discuss the stability of dilaton black holes by applying the analogous specific heat definition and remove the unstable branch by introducing a bar T = T{sub *}. It is shown that the first order phase transition temperature T{sub *} is affected by both α and n. The analogous equal area laws for both the T -δL graph and the T -δS graph are examined numerically. The relative errors for all cases are small enough so that we can safely conclude that the analogous equal area laws hold for T -δL (T -δS) graph of dilaton black holes. (orig.)
Magnetized black holes and black rings in the higher dimensional dilaton gravity
International Nuclear Information System (INIS)
Yazadjiev, Stoytcho S.
2006-01-01
In this paper we consider magnetized black holes and black rings in the higher dimensional dilaton gravity. Our study is based on exact solutions generated by applying a Harrison transformation to known asymptotically flat black hole and black ring solutions in higher dimensional spacetimes. The explicit solutions include the magnetized version of the higher dimensional Schwarzschild-Tangherlini black holes, Myers-Perry black holes, and five-dimensional (dipole) black rings. The basic physical quantities of the magnetized objects are calculated. We also discuss some properties of the solutions and their thermodynamics. The ultrarelativistic limits of the magnetized solutions are briefly discussed and an explicit example is given for the D-dimensional magnetized Schwarzschild-Tangherlini black holes
Thermodynamic instability of charged dilaton black holes in AdS spaces
International Nuclear Information System (INIS)
Sheykhi, A.; Dehghani, M. H.; Hendi, S. H.
2010-01-01
We study thermodynamic instability of a class of (n+1)-dimensional charged dilatonic spherically symmetric black holes in the background of the anti-de Sitter universe. We calculate the quasilocal mass of the anti-de Sitter dilaton black hole through the use of the subtraction method of Brown and York. We find a Smarr-type formula and perform a stability analysis in the canonical ensemble and disclose the effect of the dilaton field on the thermal stability of the solutions. Our study shows that the solutions are thermally stable for small α, while for large α the system has an unstable phase, where α is a coupling constant between the dilaton and matter field.
Critical behavior and phase transition of dilaton black holes with nonlinear electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Dayyani, Z.; Dehghani, M.H.; Hajkhalili, S. [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of); Sheykhi, A. [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of)
2018-02-15
In this paper, we take into account the dilaton black hole solutions of Einstein gravity in the presence of logarithmic and exponential forms of nonlinear electrodynamics. First of all, we consider the cosmological constant and nonlinear parameter as thermodynamic quantities which can vary. We obtain thermodynamic quantities of the system such as pressure, temperature and Gibbs free energy in an extended phase space. We complete the analogy of the nonlinear dilaton black holes with the Van der Waals liquid-gas system. We work in the canonical ensemble and hence we treat the charge of the black hole as an external fixed parameter. Moreover, we calculate the critical values of temperature, volume and pressure and show that they depend on the dilaton coupling constant as well as on the nonlinear parameter. We also investigate the critical exponents and find that they are universal and independent of the dilaton and nonlinear parameters, which is an expected result. Finally, we explore the phase transition of nonlinear dilaton black holes by studying the Gibbs free energy of the system. We find that in the case of T > T{sub c}, we have no phase transition. When T = T{sub c}, the system admits a second-order phase transition, while for T = T{sub f} < T{sub c} the system experiences a first-order transition. Interestingly, for T{sub f} < T < T{sub c} we observe a zeroth-order phase transition in the presence of a dilaton field. This novel zeroth-order phase transition occurs due to a finite jump in the Gibbs free energy which is generated by the dilaton-electromagnetic coupling constant, α, for a certain range of pressure. (orig.)
Tunneling across dilaton coupled black holes in anti de Sitter spacetime
International Nuclear Information System (INIS)
Ghosh, Tanwi; SenGupta, Soumitra
2011-01-01
Considering generalised action for dilaton coupled Maxwell-Einstein theory in four dimensions, Gao and Zhang obtained black holes solutions for asymptotically anti de Sitter (Ads) and de Sitter (ds) spacetimes. We study the Hawking radiation in Parikh-Wilczek's tunneling formalism as well as using Bogoliubov transformations. We compare the expression of the Hawking temperature obtained from these two different approaches. Stability and the extremality conditions for such black holes are discussed. The exact dependences of the Hawking temperature and flux on the dilaton coupling parameter are determined. It is shown that the Hawking flux increases with the dilaton coupling parameter. Finally we show that the expression for the Hawking flux obtained using Bogoliubov transformation matches exactly with flux calculated via chiral gauge and gravitational anomalies. This establishes a correspondence among all these different approaches of estimating Hawking radiation from these classes of black holes.
Thermodynamics of (2 +1 )-dimensional black holes in Einstein-Maxwell-dilaton gravity
Dehghani, M.
2017-08-01
In this paper, the linearly charged three-dimensional Einstein's theory coupled to a dilatonic field has been considered. It has been shown that the dilatonic potential must be considered in a form of generalized Liouville-type potential. Two new classes of charged dilatonic black hole solutions, as the exact solutions to the Einstein-Maxwell-dilaton (EMd) gravity, have been obtained and their properties have been studied. The conserved charge and mass related to both of the new EMd black holes have been calculated. Through comparison of the thermodynamical extensive quantities (i.e., temperature and entropy) obtained from both, the geometrical and the thermodynamical methods, the validity of first law of black hole thermodynamics has been investigated for both of the new black holes we just obtained. At the final stage, making use of the canonical ensemble method and regarding the black hole heat capacity, the thermal stability or phase transition of the new black hole solutions have been analyzed. It has been shown that there is a specific range for the horizon radius in such a way that the black holes with the horizon radius in that range are locally stable. Otherwise, they are unstable and may undergo type one or type two phase transitions to be stabilized.
Fermionic greybody factors of two and five-dimensional dilatonic black holes
Energy Technology Data Exchange (ETDEWEB)
Becar, Ramon [Universidad Catolica de Temuco, Departamento de Ciencias Matematicas y Fisicas, Temuco (Chile); Gonzalez, P.A. [Universidad Diego Portales, Facultad de Ingenieria, Santiago (Chile); Vasquez, Yerko [Universidad de La Serena, Departamento de Fisica, Facultad de Ciencias, La Serena (Chile)
2014-08-15
We study fermionic perturbations in the background of a two and five-dimensional dilatonic black holes. Then, we compute the reflection and transmission coefficients and the absorption cross section for fermionic fields, and we show numerically that the absorption cross section vanishes in the low and high frequency limit. Also we find that beyond a certain value of the horizon radius r{sub 0} the absorption cross section for five-dimensional dilatonic black hole is constant. Besides, we have find that the absorption cross section decreases for higher angular momentum, and it decreases when the mass of the fermionic field increases. (orig.)
Supersymmetric black holes in 2D dilaton supergravity: baldness and extremality
Energy Technology Data Exchange (ETDEWEB)
Bergamin, L; Grumiller, D; Kummer, W [Institut fuer Theoretische Physik, Technische Universitaet Wien, Wiedner Hauptstr. 8-10, A-1040 Vienna (Austria)
2004-03-26
We present a systematic discussion of supersymmetric solutions of 2D dilaton supergravity. In particular those solutions which retain at least half of the supersymmetries are ground states with respect to the bosonic Casimir function (essentially the ADM mass). Nevertheless, by tuning the prepotential appropriately, black-hole solutions may emerge with an arbitrary number of Killing horizons. The absence of dilatino and gravitino hair is proved. Moreover, the impossibility of supersymmetric dS ground states and of nonextremal black holes is confirmed, even in the presence of a dilaton. In these derivations, knowledge of the general analytic solution of 2D dilaton supergravity plays an important role. The latter result is addressed in the more general context of gPSMs which have no supergravity interpretation. Finally it is demonstrated that the inclusion of non-minimally coupled matter, a step which is already nontrivial by itself, does not change these features in an essential way.
Supersymmetric black holes in 2D dilaton supergravity: baldness and extremality
International Nuclear Information System (INIS)
Bergamin, L; Grumiller, D; Kummer, W
2004-01-01
We present a systematic discussion of supersymmetric solutions of 2D dilaton supergravity. In particular those solutions which retain at least half of the supersymmetries are ground states with respect to the bosonic Casimir function (essentially the ADM mass). Nevertheless, by tuning the prepotential appropriately, black-hole solutions may emerge with an arbitrary number of Killing horizons. The absence of dilatino and gravitino hair is proved. Moreover, the impossibility of supersymmetric dS ground states and of nonextremal black holes is confirmed, even in the presence of a dilaton. In these derivations, knowledge of the general analytic solution of 2D dilaton supergravity plays an important role. The latter result is addressed in the more general context of gPSMs which have no supergravity interpretation. Finally it is demonstrated that the inclusion of non-minimally coupled matter, a step which is already nontrivial by itself, does not change these features in an essential way
International Nuclear Information System (INIS)
Guo, Zong-Kuan; Ohta, Nobuyoshi; Torii, Takashi
2008-01-01
We study spherically symmetric, asymptotically flat black hole solutions in the low-energy effective heterotic string theory, which is the Einstein gravity with Gauss-Bonnet term and the dilaton, in various dimensions. We derive the field equations for suitable ansatz for general D dimensions and construct black hole solutions of various masses numerically in D=4,5,6 and 10 dimensional spacetime with (D-2)-dimensional hypersurface with positive constant curvature. A detailed comparison with the non-dilatonic solutions is made. We also examine the thermodynamic properties of the solutions. It is found that the dilaton has significant effects on the black hole solutions, and we discuss physical consequences. (author)
The entropy of Garfinkle-Horne dilaton black hole due to arbitrary spin fields
Institute of Scientific and Technical Information of China (English)
SHEN; Yougen(沈有根)
2002-01-01
Using the membrane model which is based on brick wall model, we calculated the free energy and entropy of Garfinkle-Horne dilatonic black hole due to arbitrary spin fields. The result shows that the entropy of scalar field and the entropy of Fermionic field have similar formulas. There is only a coefficient between them.
Iron line spectroscopy with Einstein-dilaton-Gauss-Bonnet black holes
Nampalliwar, Sourabh; Bambi, Cosimo; Kokkotas, Kostas D.; Konoplya, Roman A.
2018-06-01
Einstein-dilaton-Gauss-Bonnet gravity is a well-motivated alternative theory of gravity that emerges naturally from string theory. While black hole solutions have been known in this theory in numerical form for a while, an approximate analytical metric was obtained recently by some of us, which allows for faster and more detailed analysis. Here we test the accuracy of the analytical metric in the context of X-ray reflection spectroscopy. We analyze innermost stable circular orbits (ISCO) and relativistically broadened iron lines and find that both the ISCO and iron lines are determined sufficiently accurately up to the limit of the approximation. We also find that, though the ISCO increases by about 7% as dilaton coupling increases from zero to extremal values, the redshift at ISCO changes by less than 1%. Consequently, the shape of the iron line is much less sensitive to the dilaton charge than expected.
Abbott-Deser-Tekin Charge of Dilaton Black Holes with Squashed Horizons
Institute of Scientific and Technical Information of China (English)
Jun-Jin Peng; Wen-Chang Xiang; Shao-Hong Cai
2016-01-01
We consider the conserved charge of static black holes with squashed horizons in the Einstein-Maxwell-dilaton theory via both the Abbott-Deser-Tekin (ADT) method and its off-shell generalization.We first make use of the original ADT method to compute the mass of the dilaton squashed black holes in terms of three different reference spacetimes,which are the asymptotic geometry,the fiat background and the spacetime of the KaluzaKlein monopole with boundary matched to the original metric,respectively.Each mass satisfies the first law of black hole thermodynamics,although the mass computed on the basis of the boundary matching the KaluzaKlein monopole is different from that of the other two reference spacetimes.Then the mass of the black holes is evaluated through the off-shell generalized ADT method.
Redundant and physical black hole parameters: Is there an independent physical dilaton charge?
Directory of Open Access Journals (Sweden)
K. Hajian
2017-05-01
Full Text Available Black holes as solutions to gravity theories, are generically identified by a set of parameters. Some of these parameters are associated with black hole physical conserved charges, like ADM charges. There can also be some “redundant parameters.” We propose necessary conditions for a parameter to be physical. The conditions are essentially integrability and non-triviality of the charge variations arising from “parametric variations,” variation of the solution with respect to the chosen parameters. In addition, we prove that variation of the redundant parameters which do not meet our criteria do not appear in the first law of thermodynamics. As an interesting application, we show that dilaton moduli are redundant parameters for black hole solutions to Einstein–Maxwell–(Axion–Dilaton theories, because variations in dilaton moduli would render entropy, mass, electric charges or angular momenta non-integrable. Our results are in contrast with modification of the first law due to scalar charges suggested in Gibbons–Kallosh–Kol paper [1] and its follow-ups. We also briefly discuss implications of our results for the attractor behavior of extremal black holes.
Redundant and physical black hole parameters: Is there an independent physical dilaton charge?
Energy Technology Data Exchange (ETDEWEB)
Hajian, K., E-mail: kamalhajian@ipm.ir; Sheikh-Jabbari, M.M., E-mail: jabbari@theory.ipm.ac.ir
2017-05-10
Black holes as solutions to gravity theories, are generically identified by a set of parameters. Some of these parameters are associated with black hole physical conserved charges, like ADM charges. There can also be some “redundant parameters.” We propose necessary conditions for a parameter to be physical. The conditions are essentially integrability and non-triviality of the charge variations arising from “parametric variations,” variation of the solution with respect to the chosen parameters. In addition, we prove that variation of the redundant parameters which do not meet our criteria do not appear in the first law of thermodynamics. As an interesting application, we show that dilaton moduli are redundant parameters for black hole solutions to Einstein–Maxwell–(Axion)–Dilaton theories, because variations in dilaton moduli would render entropy, mass, electric charges or angular momenta non-integrable. Our results are in contrast with modification of the first law due to scalar charges suggested in Gibbons–Kallosh–Kol paper and its follow-ups. We also briefly discuss implications of our results for the attractor behavior of extremal black holes.
Total Energy of Charged Black Holes in Einstein-Maxwell-Dilaton-Axion Theory
Directory of Open Access Journals (Sweden)
Murat Korunur
2012-01-01
Full Text Available We focus on the energy content (including matter and fields of the Møller energy-momentum complex in the framework of Einstein-Maxwell-Dilaton-Axion (EMDA theory using teleparallel gravity. We perform the required calculations for some specific charged black hole models, and we find that total energy distributions associated with asymptotically flat black holes are proportional to the gravitational mass. On the other hand, we see that the energy of the asymptotically nonflat black holes diverge in a limiting case.
Directory of Open Access Journals (Sweden)
A. Sheykhi
2016-01-01
Full Text Available We construct a new class of charged rotating black brane solutions in the presence of logarithmic nonlinear electrodynamics with complete set of the rotation parameters in arbitrary dimensions. The topology of the horizon of these rotating black branes is flat, while due to the presence of the dilaton field the asymptotic behavior of them is neither flat nor (anti-de Sitter [(AdS]. We investigate the physical properties of the solutions. The mass and angular momentum of the spacetime are obtained by using the counterterm method inspired by AdS/CFT correspondence. We derive temperature, electric potential, and entropy associated with the horizon and check the validity of the first law of thermodynamics on the black brane horizon. We study thermal stability of the solutions in both canonical and grand-canonical ensemble and disclose the effects of the rotation parameter, nonlinearity of electrodynamics, and dilaton field on the thermal stability conditions. We find the solutions are thermally stable for α1 the solutions may encounter an unstable phase, where α is dilaton-electromagnetic coupling constant.
Radiating black holes in Einstein-Maxwell-dilaton theory and cosmic censorship violation
International Nuclear Information System (INIS)
Aniceto, Pedro; Pani, Paolo; Rocha, Jorge V.
2016-01-01
We construct exact, time-dependent, black hole solutions of Einstein-Maxwell-dilaton theory with arbitrary dilaton coupling, a. For a=1 this theory arises as the four-dimensional low-energy effective description of heterotic string theory. These solutions represent electrically charged, spherically symmetric black holes emitting or absorbing charged null fluids and generalize the Vaidya and Bonnor-Vaidya solutions of general relativity and of Einstein-Maxwell theory, respectively. The a=1 case stands out as special, in the sense that it is the only choice of the coupling that allows for a time-dependent dilaton field in this class of solutions. As a by-product, when a=1 we show that an electrically charged black hole in this theory can be overcharged by bombarding it with a stream of electrically charged null fluid, resulting in the formation of a naked singularity. This provides an example of cosmic censorship violation in an exact dynamical solution to low-energy effective string theory and in a case in which the total stress-energy tensor satisfies all energy conditions. When a≠1, our solutions necessarily have a time-independent scalar field and consequently cannot be overcharged.
Radiating black holes in Einstein-Maxwell-dilaton theory and cosmic censorship violation
Energy Technology Data Exchange (ETDEWEB)
Aniceto, Pedro [CENTRA, Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa,Avenida Rovisco Pais 1, 1049 Lisboa (Portugal); Pani, Paolo [Dipartimento di Fisica, “Sapienza” Università di Roma & Sezione INFN Roma 1,Piazzale Aldo Moro 5, 00185 Roma (Italy); CENTRA, Departamento de Física, Instituto Superior Técnico, Universidade de Lisboa,Avenida Rovisco Pais 1, 1049 Lisboa (Portugal); Rocha, Jorge V. [Departament de Física Fonamental, Institut de Ciències del Cosmos (ICCUB),Universitat de Barcelona,Martí i Franquès 1, E-08028 Barcelona (Spain)
2016-05-19
We construct exact, time-dependent, black hole solutions of Einstein-Maxwell-dilaton theory with arbitrary dilaton coupling, a. For a=1 this theory arises as the four-dimensional low-energy effective description of heterotic string theory. These solutions represent electrically charged, spherically symmetric black holes emitting or absorbing charged null fluids and generalize the Vaidya and Bonnor-Vaidya solutions of general relativity and of Einstein-Maxwell theory, respectively. The a=1 case stands out as special, in the sense that it is the only choice of the coupling that allows for a time-dependent dilaton field in this class of solutions. As a by-product, when a=1 we show that an electrically charged black hole in this theory can be overcharged by bombarding it with a stream of electrically charged null fluid, resulting in the formation of a naked singularity. This provides an example of cosmic censorship violation in an exact dynamical solution to low-energy effective string theory and in a case in which the total stress-energy tensor satisfies all energy conditions. When a≠1, our solutions necessarily have a time-independent scalar field and consequently cannot be overcharged.
Chern–Simons dilaton black holes in 2 + 1 dimensions
International Nuclear Information System (INIS)
Moussa, Karim Ait; Clément, Gérard; Guennoune, Hakim
2016-01-01
We construct rotating magnetic solutions to the three-dimensional Einstein–Maxwell–Chern–Simons-dilaton theory with a Liouville potential. These include a class of black hole solutions which generalize the warped AdS black holes. The regular black holes belong to two disjointed sectors. The first sector includes black holes which have a positive mass and are co-rotating, while the black holes of the second sector have a negative mass and are counter-rotating. We also show that a particular, non-black hole, subfamily of our three-dimensional solutions may be uplifted to new regular non-asymptotically flat solutions of five-dimensional Einstein–Maxwell–Chern–Simons theory. (paper)
International Nuclear Information System (INIS)
Pani, Paolo; Cardoso, Vitor
2009-01-01
It is generally accepted that Einstein's theory will get some as yet unknown corrections, possibly large in the strong-field regime. An ideal place to look for these modifications is in the vicinities of compact objects such as black holes. Here, we study dilatonic black holes, which arise in the framework of Gauss-Bonnet couplings and one-loop corrected four-dimensional effective theory of heterotic superstrings at low energies. These are interesting objects as a prototype for alternative, yet well-behaved gravity theories: they evade the 'no-hair' theorem of general relativity but were proven to be stable against radial perturbations. We investigate the viability of these black holes as astrophysical objects and try to provide some means to distinguish them from black holes in general relativity. We start by extending previous works and establishing the stability of these black holes against axial perturbations. We then look for solutions of the field equations describing slowly rotating black holes and study geodesic motion around this geometry. Depending on the values of mass, dilaton charge, and angular momentum of the solution, one can have differences in the innermost-stable-circular-orbit location and orbital frequency, relative to black holes in general relativity. In the most favorable cases, the difference amounts to a few percent. Given the current state-of-the-art, we discuss the difficulty of distinguishing the correct theory of gravity from electromagnetic observations or even with gravitational-wave detectors.
Two-Phase Equilibrium Properties in Charged Topological Dilaton AdS Black Holes
Directory of Open Access Journals (Sweden)
Hui-Hua Zhao
2016-01-01
Full Text Available We discuss phase transition of the charged topological dilaton AdS black holes by Maxwell equal area law. The two phases involved in the phase transition could coexist and we depict the coexistence region in P-v diagrams. The two-phase equilibrium curves in P-T diagrams are plotted, the Clapeyron equation for the black hole is derived, and the latent heat of isothermal phase transition is investigated. We also analyze the parameters of the black hole that could have an effect on the two-phase coexistence. The results show that the black holes may go through a small-large phase transition similar to that of a usual nongravity thermodynamic system.
Energy Technology Data Exchange (ETDEWEB)
Becar, Ramon [Universidad Catolica de Temuco, Departamento de Ciencias Matematicas y Fisicas, Temuco (Chile); Gonzalez, P.A. [Universidad Diego Portales, Facultad de Ingenieria, Santiago (Chile); Saavedra, Joel [Pontificia Universidad Catolica de Valparaiso, Instituto de Fisica, Valparaiso (Chile); Vasquez, Yerko [Universidad de La Serena, Departamento de Fisica, Facultad de Ciencias, La Serena (Chile)
2015-02-01
We study massive charged fermionic perturbations in the background of a charged two-dimensional dilatonic black hole, and we solve the Dirac equation analytically. Then we compute the reflection and transmission coefficients and the absorption cross section for massive charged fermionic fields, and we show that the absorption cross section vanishes at the low- and high-frequency limits. However, there is a range of frequencies where the absorption cross section is not null. Furthermore, we study the effect of the mass and electric charge of the fermionic field over the absorption cross section. (orig.)
Thermodynamics of charged rotating dilaton black branes with power-law Maxwell field
International Nuclear Information System (INIS)
Zangeneh, M.K.; Sheykhi, A.; Dehghani, M.H.
2015-01-01
In this paper, we construct a new class of charged rotating dilaton black brane solutions, with a complete set of rotation parameters, which is coupled to a nonlinear Maxwell field. The Lagrangian of the matter field has the form of the power-law Maxwell field. We study the causal structure of the spacetime and its physical properties in ample details. We also compute thermodynamic and conserved quantities of the spacetime, such as the temperature, entropy, mass, charge, and angular momentum. We find a Smarr-formula for the mass and verify the validity of the first law of thermodynamics on the black brane horizon. Finally, we investigate the thermal stability of solutions in both the canonical and the grand-canonical ensembles and disclose the effects of dilaton field and nonlinearity of the Maxwell field on the thermal stability of the solutions. We find that, for α ≤ 1, charged rotating black brane solutions are thermally stable independent of the values of the other parameters. For α > 1, the solutions can encounter an unstable phase depending on the metric parameters. (orig.)
Lifshitz black branes and DC transport coefficients in massive Einstein-Maxwell-dilaton gravity
Kuang, Xiao-Mei; Papantonopoulos, Eleftherios; Wu, Jian-Pin; Zhou, Zhenhua
2018-03-01
We construct analytical Lifshitz massive black brane solutions in massive Einstein-Maxwell-dilaton gravity theory. We also study the thermodynamics of these black brane solutions and obtain the thermodynamical stability conditions. On the dual nonrelativistic boundary field theory with Lifshitz symmetry, we analytically compute the DC transport coefficients, including the electric conductivity, thermoelectric conductivity, and thermal conductivity. The novel property of our model is that the massive term supports the Lifshitz black brane solutions with z ≠1 in such a way that the DC transport coefficients in the dual field theory are finite. We also find that the Wiedemann-Franz law in this dual boundary field theory is violated, which indicates that it may involve strong interactions.
Dilatonic dyon-like black hole solutions in the model with two Abelian gauge fields
Energy Technology Data Exchange (ETDEWEB)
Abishev, M.E. [Institute of Experimental and Theoretical Physics, Al-Farabi Kazakh National University, Almaty (Kazakhstan); Institute of Gravitation and Cosmology, RUDN University, Moscow (Russian Federation); Boshkayev, K.A. [Institute of Experimental and Theoretical Physics, Al-Farabi Kazakh National University, Almaty (Kazakhstan); Ivashchuk, V.D. [Center for Gravitation and Fundamental Metrology, VNIIMS, Moscow (Russian Federation); Institute of Gravitation and Cosmology, RUDN University, Moscow (Russian Federation)
2017-03-15
Dilatonic black hole dyon-like solutions in the gravitational 4d model with a scalar field, two 2-forms, two dilatonic coupling constants λ{sub i} ≠ 0, i = 1,2, obeying λ{sub 1} ≠ -λ{sub 2} and the sign parameter ε = ±1 for scalar field kinetic term are considered. Here ε = -1 corresponds to a ghost scalar field. These solutions are defined up to solutions of two master equations for two moduli functions, when λ{sup 2}{sub i} ≠ 1/2 for ε = -1. Some physical parameters of the solutions are obtained: gravitational mass, scalar charge, Hawking temperature, black hole area entropy and parametrized post-Newtonian (PPN) parameters β and γ. The PPN parameters do not depend on the couplings λ{sub i} and ε. A set of bounds on the gravitational mass and scalar charge are found by using a certain conjecture on the parameters of solutions, when 1 + 2λ{sub i}{sup 2} ε > 0, i = 1,2. (orig.)
Fujisaki, H
2003-01-01
Microcanonical ensemble paradigm is described in proper reference to the thermal aspect of the extremal state for a dilute gas of charged rotating black holes coupled to a dilaton field on the basis of the boosted Kerr solution of the Kaluza-Klein theory.
Energy Technology Data Exchange (ETDEWEB)
Hendi, S.H. [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); Panah, B.E. [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); ICRANet, Pescara (Italy); Panahiyan, S. [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of); Helmholtz-Institut Jena, Jena (Germany); Shahid Beheshti University, Physics Department, Tehran (Iran, Islamic Republic of); Momennia, M. [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of)
2017-09-15
This paper is devoted to an investigation of nonlinearly charged dilatonic black holes in the context of gravity's rainbow with two cases: (1) by considering the usual entropy, (2) in the presence of first order logarithmic correction of the entropy. First, exact black hole solutions of dilatonic Born-Infeld gravity with an energy dependent Liouville-type potential are obtained. Then, thermodynamic properties of the mentioned cases are studied, separately. It will be shown that although mass, entropy and the heat capacity are modified due to the presence of a first order correction, the temperature remains independent of it. Furthermore, it will be shown that divergences of the heat capacity, hence phase transition points are also independent of a first order correction, whereas the stability conditions are highly sensitive to variation of the correction parameter. Except for the effects of a first order correction, we will also present a limit on the values of the dilatonic parameter and show that it is possible to recognize AdS and dS thermodynamical behaviors for two specific branches of the dilatonic parameter. In addition, the effects of nonlinear electromagnetic field and energy functions on the thermodynamical behavior of the solutions will be highlighted and dependency of critical behavior, on these generalizations will be investigated. (orig.)
International Nuclear Information System (INIS)
Hendi, S.H.; Panah, B.E.; Panahiyan, S.; Momennia, M.
2017-01-01
This paper is devoted to an investigation of nonlinearly charged dilatonic black holes in the context of gravity's rainbow with two cases: (1) by considering the usual entropy, (2) in the presence of first order logarithmic correction of the entropy. First, exact black hole solutions of dilatonic Born-Infeld gravity with an energy dependent Liouville-type potential are obtained. Then, thermodynamic properties of the mentioned cases are studied, separately. It will be shown that although mass, entropy and the heat capacity are modified due to the presence of a first order correction, the temperature remains independent of it. Furthermore, it will be shown that divergences of the heat capacity, hence phase transition points are also independent of a first order correction, whereas the stability conditions are highly sensitive to variation of the correction parameter. Except for the effects of a first order correction, we will also present a limit on the values of the dilatonic parameter and show that it is possible to recognize AdS and dS thermodynamical behaviors for two specific branches of the dilatonic parameter. In addition, the effects of nonlinear electromagnetic field and energy functions on the thermodynamical behavior of the solutions will be highlighted and dependency of critical behavior, on these generalizations will be investigated. (orig.)
International Nuclear Information System (INIS)
Das, S.R.; Mukherji, S.
1994-01-01
We study black hole formation in a model of two dimensional dilaton gravity and 24 massless scalar fields with a boundary. We find the most general boundary condition consistent with perfect reflection of matter and the constraints. We show that in the semiclassical approximation and for the generic value of a parameter which characterizes the boundary conditions, the boundary starts receding to infinity at the speed of light whenever the total energy of the incoming matter flux exceeds a certain critical value. This is also the critical energy which marks the onset of black hole formation. We then compute the quantum fluctuations of the boundary and of the rescaled scalar curvature and show that as soon as the incoming energy exceeds this critical value, and asymptotic observer using normal time resolutions will always measure large quantum fluctuations of space-time near the horizon, even though the freely falling observer does not. This is an aspect of black hole complementarity relating directly to quantum gravity effects. (author). 30 refs, 4 figs
Blázquez-Salcedo, Jose Luis
2016-01-01
Gravitational waves emitted by distorted black holes---such as those arising from the coalescence of two neutron stars or black holes---carry not only information about the corresponding spacetime but also about the underlying theory of gravity. Although general relativity remains the simplest, most elegant and viable theory of gravitation, there are generic and robust arguments indicating that it is not the ultimate description of the gravitational universe. Here we focus on a particularly appealing extension of general relativity, which corrects Einstein's theory through the addition of terms which are second order in curvature: the topological Gauss-Bonnet invariant coupled to a dilaton. We study gravitational-wave emission from black holes in this theory, and (i) find strong evidence that black holes are linearly (mode) stable against both axial and polar perturbations; (ii) discuss how the quasinormal modes of black holes can be excited during collisions involving black holes, and finally (iii) show that...
Energy Technology Data Exchange (ETDEWEB)
Rogatko, Marek [Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin (Poland)
2002-07-21
We derive general formulae for the first-order variation of the ADM mass and angular momentum for the linear perturbations of a stationary background in Einstein-Maxwell axion-dilaton gravity which is the low-energy limit of the heterotic string theory. All these variations were expressed in terms of the perturbed matter energy-momentum tensor and the perturbed charge current density. Combining these expressions, we reached at the form of the physical process version of the first law of black-hole dynamics for the stationary black holes in the considered theory which is a strong support for the cosmic censorship hypothesis.
Extremal dyonic black holes in D=4 Gauss-Bonnet gravity
International Nuclear Information System (INIS)
Chen, C.-M.; Gal'tsov, Dmitri V.; Orlov, Dmitry G.
2008-01-01
We investigate extremal dyon black holes in the Einstein-Maxwell-dilaton theory with higher curvature corrections in the form of the Gauss-Bonnet density coupled to the dilaton. In the same theory without the Gauss-Bonnet term the extremal dyon solutions exist only for discrete values of the dilaton coupling constant a. We show that the Gauss-Bonnet term acts as a dyon hair tonic enlarging the allowed values of a to continuous domains in the plane (a,q m ) where q m is the magnetic charge. In the limit of the vanishing curvature coupling (a large magnetic charge) the dyon solutions obtained tend to the Reissner-Nordstroem solution but not to the extremal dyons of the Einstein-Maxwell-dilaton theory. Both solutions have the same dependence of the horizon radius in terms of charges. The entropy of new dyonic black holes interpolates between the Bekenstein-Hawking value in the limit of the large magnetic charge (equivalent to the vanishing Gauss-Bonnet coupling) and twice this value for the vanishing magnetic charge. Although an expression for the entropy can be obtained analytically using purely local near-horizon solutions, its interpretation as the black hole entropy is legitimate only once the global black hole solution is known to exist, and we obtain numerically the corresponding conditions on the parameters. Thus, a purely local analysis is insufficient to fully understand the entropy of the curvature-corrected black holes. We also find dyon solutions which are not asymptotically flat, but approach the linear dilaton background at infinity. They describe magnetic black holes on the electric linear dilaton background.
Black hole physics from two-dimensional dilaton gravity based on the SL(2,R)/U(1) coset model
International Nuclear Information System (INIS)
Nojiri, S.; Oda, I.
1994-01-01
We analyze the quantum two-dimensional dilaton gravity model, which is described by the SL(2,R)/U(1) gauged Wess-Zumino-Witten model deformed by a (1,1) operator. We show that the curvature singularity does not appear when the central charge c matter of the matter fields is given by 22 matter matter matter ∝δ(x + -x 0 + ), create a kind of wormholes, i.e., causally disconnected regions. Most of the quantum information in past null infinity is lost in future null infinity but the lost information would be carried by the wormholes. We also discuss the problem of defining the mass of quantum black holes. On the basis of the argument by Regge and Teitelboim, we show that the ADM mass measured by the observer who lives in one of the asymptotically flat regions is finite and does not vanish in general. On the other hand, the Bondi mass is ill defined in this model. Instead of the Bondi mass, we consider the mass measured by observers who live in an asymptotically flat region at first. A class of observers finds the mass of the black hole created by a shock wave changes as the observers' proper time goes by, i.e., they observe Hawking radiation. The measured mass vanishes after the infinite proper time and the black hole evaporates completely. Therefore the total Hawking radiation is positive even when N<24
Stringy stability of charged dilaton black holes with flat event horizon
Energy Technology Data Exchange (ETDEWEB)
Ong, Yen Chin [National Taiwan Univ., Taipei (Taiwan); Chen, Pisin [National Taiwan Univ., Taipei (Taiwan); SLAC National Accelerator Lab., Menlo Park, CA (United States)
2015-01-15
Electrically charged black holes with flat event horizon in anti-de Sitter space have received much attention due to various applications in Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence, from modeling the behavior of quark-gluon plasma to superconductor. Critical to the physics on the dual field theory is the fact that when embedded in string theory, black holes in the bulk may become vulnerable to instability caused by brane pair-production. Since dilation arises naturally in the context of string theory, we study the effect of coupling dilation to Maxwell field on the stability of flat charged AdS black holes.
Energy Technology Data Exchange (ETDEWEB)
Hendi, S.H. [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), P. O. Box 55134-441, Maragha (Iran, Islamic Republic of); Tad, R.M.; Armanfard, Z.; Talezadeh, M.S. [Shiraz University, Physics Department and Biruni Observatory, College of Sciences, Shiraz (Iran, Islamic Republic of)
2016-05-15
Motivated by a thermodynamic analogy of black holes and Van der Waals liquid/gas systems, in this paper, we study P-V criticality of both dilatonic Born-Infeld black holes and their conformal solutions, Brans-Dicke-Born-Infeld solutions. Due to the conformal constraint, we have to neglect the old Lagrangian of dilatonic Born-Infeld theory and its black hole solutions, and introduce a new one. We obtain spherically symmetric nonlinearly charged black hole solutions in both Einstein and Jordan frames and then we calculate the related conserved and thermodynamic quantities. After that, we extend the phase space by considering the proportionality of the cosmological constant and thermodynamical pressure. We obtain critical values of the thermodynamic coordinates through numerical methods and plot the relevant P-V and G-T diagrams. Investigation of the mentioned diagrams helps us to study the thermodynamical phase transition. We also analyze the effects of varying different parameters on the phase transition of black holes. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Li, Huai-Fan; Zhao, Hui-Hua; Zhang, Li-Chun; Zhao, Ren [Shanxi Datong University, Institute of Theoretical Physics, Datong (China); Shanxi Datong University, Department of Physics, Datong (China)
2017-05-15
Using Maxwell's equal area law, we discuss the phase transition of higher dimensional charged topological dilaton AdS black hole with a nonlinear source. The coexisting region of the two phases is found and we depict the coexistence region in the P-v diagrams. The two-phase equilibrium curves in the P-T diagrams are plotted, and we take the first order approximation of volume v in the calculation. To better compare with a general thermodynamic system, the Clapeyron equation is derived for a higher dimensional charged topological black hole with a nonlinear source. The latent heat of an isothermal phase transition is investigated. We also study the effect of the parameters of the black hole on the region of two-phase coexistence. The results show that the black hole may go through a small-large phase transition similar to those of usual non-gravity thermodynamic systems. (orig.)
Conservation laws and two-dimensional black holes in dilaton gravity
Mann, R. B.
1993-05-01
A very general class of Lagrangians which couple scalar fields to gravitation and matter in two spacetime dimensions is investigated. It is shown that a vector field exists along whose flow lines the stress-energy tensor is conserved, regardless of whether or not the equations of motion are satisfied or if any Killing vectors exist. Conditions necessary for the existence of Killing vectors are derived. A new set of two-dimensional (2D) black-hole solutions is obtained for one particular member within this class of Lagrangians, which couples a Liouville field to 2D gravity in a novel way. One solution of this theory bears an interesting resemblance to the 2D string-theoretic black hole, yet contains markedly different thermodynamic properties.
Cosmic censorship and the dilaton
International Nuclear Information System (INIS)
Horne, J.H.; Horowitz, G.T.
1993-01-01
We investigate extremal electrically charged black holes in Einstein-Maxwell-dilaton theory with a cosmological constant inspired by string theory. These solutions are not static, and a timelike singularity eventually appears which is not surrounded by an event horizon. This suggests that cosmic censorship may be violated in this theory
The no-hair conjecture in 2D dilaton supergravity
International Nuclear Information System (INIS)
Gamboa, J.; Georgelin, Y.
1993-06-01
Two dimensional dilaton gravity and supergravity are studied following Hamiltonian methods. The structure of constraints of 2D dilaton gravity and the 2D dilaton supergravity theory is discussed taking the square root of the bosonic constraints. The equations of motion are integrated in both cases, and it is shown that the solutions of the equation of motion of 2D dilaton supergravity differs from the solutions of 2D dilaton gravity only by boundary conditions on the fermionic variables, i.e. the black holes of 2D dilaton supergravity theory are exactly the same black holes of 2D bosonic dilaton gravity modulo supersymmetry transformations. This result is the bidimensional analogue of the no-hair theorem for supergravity. (authors). 28 refs
International Nuclear Information System (INIS)
Zangeneh, M.K.; Dehyadegari, A.; Mehdizadeh, M.R.; Wang, B.; Sheykhi, A.
2017-01-01
In this paper, we first obtain the higher-dimen-sional dilaton-Lifshitz black hole solutions in the presence of Born-Infeld (BI) electrodynamics. We find that there are two different solutions for the cases of z = n + 1 and z ≠ n + 1 where z is the dynamical critical exponent and n is the number of spatial dimensions. Calculating the conserved and thermodynamical quantities, we show that the first law of thermodynamics is satisfied for both cases. Then we turn to the study of different phase transitions for our Lifshitz black holes. We start with the Hawking-Page phase transition and explore the effects of different parameters of our model on it for both linearly and BI charged cases. After that, we discuss the phase transitions inside the black holes. We present the improved Davies quantities and prove that the phase transition points shown by them are coincident with the Ruppeiner ones. We show that the zero temperature phase transitions are transitions in the radiance properties of black holes by using the Landau-Lifshitz theory of thermodynamic fluctuations. Next, we turn to the study of the Ruppeiner geometry (thermodynamic geometry) for our solutions. We investigate thermal stability, interaction type of possible black hole molecules and phase transitions of our solutions for linearly and BI charged cases separately. For the linearly charged case, we show that there are no phase transitions at finite temperature for the case z ≥ 2. For z < 2, it is found that the number of finite temperature phase transition points depends on the value of the black hole charge and there are not more than two. When we have two finite temperature phase transition points, there is no thermally stable black hole between these two points and we have discontinuous small/large black hole phase transitions. As expected, for small black holes, we observe finite magnitude for the Ruppeiner invariant, which shows the finite correlation between possible black hole molecules, while
Energy Technology Data Exchange (ETDEWEB)
Zangeneh, M.K. [Shanghai Jiao Tong University, Department of Physics and Astronomy, Center of Astronomy and Astrophysics, Shanghai (China); Shiraz University, Physics Department and Biruni Observatory, Shiraz (Iran, Islamic Republic of); Shahid Chamran University of Ahvaz, Physics Department, Faculty of Science, Ahvaz (Iran, Islamic Republic of); Dehyadegari, A. [Shiraz University, Physics Department and Biruni Observatory, Shiraz (Iran, Islamic Republic of); Mehdizadeh, M.R. [Shahid Bahonar University, Department of Physics, P.O. Box 76175, Kerman (Iran, Islamic Republic of); Research Institute for Astrophysics and Astronomy of Maragha (RIAAM), P.O. Box 55134-441, Maragha (Iran, Islamic Republic of); Wang, B. [Shanghai Jiao Tong University, Department of Physics and Astronomy, Center of Astronomy and Astrophysics, Shanghai (China); Sheykhi, A. [Shiraz University, Physics Department and Biruni Observatory, Shiraz (Iran, Islamic Republic of); Research Institute for Astrophysics and Astronomy of Maragha (RIAAM), P.O. Box 55134-441, Maragha (Iran, Islamic Republic of)
2017-06-15
In this paper, we first obtain the higher-dimen-sional dilaton-Lifshitz black hole solutions in the presence of Born-Infeld (BI) electrodynamics. We find that there are two different solutions for the cases of z = n + 1 and z ≠ n + 1 where z is the dynamical critical exponent and n is the number of spatial dimensions. Calculating the conserved and thermodynamical quantities, we show that the first law of thermodynamics is satisfied for both cases. Then we turn to the study of different phase transitions for our Lifshitz black holes. We start with the Hawking-Page phase transition and explore the effects of different parameters of our model on it for both linearly and BI charged cases. After that, we discuss the phase transitions inside the black holes. We present the improved Davies quantities and prove that the phase transition points shown by them are coincident with the Ruppeiner ones. We show that the zero temperature phase transitions are transitions in the radiance properties of black holes by using the Landau-Lifshitz theory of thermodynamic fluctuations. Next, we turn to the study of the Ruppeiner geometry (thermodynamic geometry) for our solutions. We investigate thermal stability, interaction type of possible black hole molecules and phase transitions of our solutions for linearly and BI charged cases separately. For the linearly charged case, we show that there are no phase transitions at finite temperature for the case z ≥ 2. For z < 2, it is found that the number of finite temperature phase transition points depends on the value of the black hole charge and there are not more than two. When we have two finite temperature phase transition points, there is no thermally stable black hole between these two points and we have discontinuous small/large black hole phase transitions. As expected, for small black holes, we observe finite magnitude for the Ruppeiner invariant, which shows the finite correlation between possible black hole molecules, while
Higher curvature corrections to primordial fluctuations in slow-roll inflation
International Nuclear Information System (INIS)
Satoh, Masaki; Soda, Jiro
2008-01-01
We study higher curvature corrections to the scalar spectral index, the tensor spectral index, the tensor-to-scalar ratio, and the polarization of gravitational waves. We find that there are cases where the higher curvature corrections cannot be negligible in the dynamics of the scalar field, although they are always negligible energetically. Indeed, it turns out that the tensor-to-scalar ratio could be enhanced and the tensor spectral index could be blue due to the Gauss–Bonnet term. We estimate the degree of circular polarization of gravitational waves generated during the slow-roll inflation. We argue that the circular polarization could be observable with the help of both the Gauss–Bonnet and the parity violating terms. We also present several examples to reveal observational implications of higher curvature corrections for chaotic inflationary models
Dilatonic imprints on exact gravitational wave signatures
McCarthy, Fiona; KubizÅák, David; Mann, Robert B.
2018-05-01
By employing the moduli space approximation, we analytically calculate the gravitational wave signatures emitted upon the merger of two extremally charged dilatonic black holes. We probe several values of the dilatonic coupling constant a , and find significant departures from the Einstein-Maxwell (a =0 ) counterpart studied in [Phys. Rev. D 96, 061501 (2017), 10.1103/PhysRevD.96.061501]. For (low-energy) string theory black holes (a =1 ) there are no coalescence orbits and only a memory effect is observed, whereas for an intermediate value of the coupling (a =1 /√{3 } ) the late-time merger signature becomes exponentially suppressed, compared to the polynomial decay in the a =0 case without a dilaton. Such an imprint shows a clear difference between the case with and without a scalar field (as, for example, predicted by string theory) in black hole mergers.
Trace Anomaly of Dilaton Coupled Scalars in Two Dimensions
Bousso, Raphael; Hawking, Stephen
1997-01-01
Conformal scalar fields coupled to the dilaton appear naturally in two-dimensional models of black hole evaporation. We calculate their trace anomaly. It follows that an RST-type counterterm appears naturally in the one-loop effective action.
Entropy function and universality of entropy-area relation for small black holes
International Nuclear Information System (INIS)
Cai Ronggen; Chen, C.-M.; Maeda, Kei-ichi; Ohta, Nobuyoshi; Pang Dawei
2008-01-01
We discuss the entropy-area relation for the small black holes with higher curvature corrections by using the entropy function formalism and field redefinition method. We show that the entropy S BH of the small black hole is proportional to its horizon area A. In particular, we find a universal result that S BH =A/2G, the ratio is 2 times of Bekenstein-Hawking entropy-area formula in many cases of physical interest. In four dimensions, the universal relation is always true irrespective of the coefficients of the higher-order terms if the dilaton couplings are the same, which is the case for string effective theory, while in five dimensions, the relation again holds irrespective of the overall coefficient if the higher-order corrections are in the GB combination. We also discuss how this result generalizes to known physically interesting cases with Lovelock correction terms in various dimensions, and possible implications of the universal relation.
Numerical calculation of the entanglement entropy for scalar field in dilaton spacetimes
Huang, Shifeng; Fang, Xiongjun; Jing, Jiliang
2018-06-01
Using coupled harmonic oscillators model, we numerical analyze the entanglement entropy of massless scalar field in Gafinkle-Horowitz-Strominger (GHS) dilaton spacetime and Gibbons-Maeda (GM) dilaton spacetime. By numerical fitting, we find that the entanglement entropy of the dilaton black holes receive contribution from dilaton charge and is proportional to the area of the event horizon. It is interesting to note that the results of numerical fitting are coincide with ones obtained by using brick wall method and Euclidean path integral approach.
Curvature correction of retinal OCTs using graph-based geometry detection
Kafieh, Raheleh; Rabbani, Hossein; Abramoff, Michael D.; Sonka, Milan
2013-05-01
In this paper, we present a new algorithm as an enhancement and preprocessing step for acquired optical coherence tomography (OCT) images of the retina. The proposed method is composed of two steps, first of which is a denoising algorithm with wavelet diffusion based on a circular symmetric Laplacian model, and the second part can be described in terms of graph-based geometry detection and curvature correction according to the hyper-reflective complex layer in the retina. The proposed denoising algorithm showed an improvement of contrast-to-noise ratio from 0.89 to 1.49 and an increase of signal-to-noise ratio (OCT image SNR) from 18.27 to 30.43 dB. By applying the proposed method for estimation of the interpolated curve using a full automatic method, the mean ± SD unsigned border positioning error was calculated for normal and abnormal cases. The error values of 2.19 ± 1.25 and 8.53 ± 3.76 µm were detected for 200 randomly selected slices without pathological curvature and 50 randomly selected slices with pathological curvature, respectively. The important aspect of this algorithm is its ability in detection of curvature in strongly pathological images that surpasses previously introduced methods; the method is also fast, compared to the relatively low speed of similar methods.
Curvature correction of retinal OCTs using graph-based geometry detection
International Nuclear Information System (INIS)
Kafieh, Raheleh; Rabbani, Hossein; Abramoff, Michael D; Sonka, Milan
2013-01-01
In this paper, we present a new algorithm as an enhancement and preprocessing step for acquired optical coherence tomography (OCT) images of the retina. The proposed method is composed of two steps, first of which is a denoising algorithm with wavelet diffusion based on a circular symmetric Laplacian model, and the second part can be described in terms of graph-based geometry detection and curvature correction according to the hyper-reflective complex layer in the retina. The proposed denoising algorithm showed an improvement of contrast-to-noise ratio from 0.89 to 1.49 and an increase of signal-to-noise ratio (OCT image SNR) from 18.27 to 30.43 dB. By applying the proposed method for estimation of the interpolated curve using a full automatic method, the mean ± SD unsigned border positioning error was calculated for normal and abnormal cases. The error values of 2.19 ± 1.25 and 8.53 ± 3.76 µm were detected for 200 randomly selected slices without pathological curvature and 50 randomly selected slices with pathological curvature, respectively. The important aspect of this algorithm is its ability in detection of curvature in strongly pathological images that surpasses previously introduced methods; the method is also fast, compared to the relatively low speed of similar methods. (paper)
A Remark on Dilaton Stabilization
Dvali, Gia; Dvali, Gia; Kakushadze, Zurab
1998-01-01
Dilaton stabilization may occur in a theory based on a single asymptotically free gauge group with matter due to an interplay between quantum modification of the moduli space and tree-level superpotential. We present a toy model where such a mechanism is realized. Dilaton stabilization in this mechanism tends to occur at strong coupling values unless some unnatural adjustment of parameters is involved.
Coupled dilaton and electromagnetic field in cylindrically symmetric ...
Indian Academy of Sciences (India)
The dilaton black hole solutions have attracted considerable attention for the ... theory and study the corresponding cylindrically symmetric spacetime, where .... where Йm and Йe are integration constants to be interpreted later as the ..... feature is apparent for the cylindrically symmetric spacetime in the presence of the dila-.
Directory of Open Access Journals (Sweden)
Oda Kin-ya
2013-05-01
Full Text Available Both the ATLAS and CMS experiments at the LHC have reported the observation of the particle of mass around 125 GeV which is consistent to the Standard Model (SM Higgs boson, but with an excess of events beyond the SM expectation in the diphoton decay channel at each of them. There still remains room for a logical possibility that we are not seeing the SM Higgs but something else. Here we introduce the minimal dilaton model in which the LHC signals are explained by an extra singlet scalar of the mass around 125 GeV that slightly mixes with the SM Higgs heavier than 600 GeV. When this scalar has a vacuum expectation value well beyond the electroweak scale, it can be identified as a linearly realized version of a dilaton field. Though the current experimental constraints from the Higgs search disfavors such a region, the singlet scalar model itself still provides a viable alternative to the SM Higgs in interpreting its search results.
Cosmic censorship and Weak Gravity Conjecture in the Einstein-Maxwell-dilaton theory
Yu, Ten-Yeh; Wen, Wen-Yu
2018-06-01
We explore the cosmic censorship in the Einstein-Maxwell-dilaton theory following Wald's thought experiment to destroy a black hole by throwing in a test particle. We discover that at probe limit the extremal charged dilaton black hole could be destroyed by a test particle with specific energy. Nevertheless the censorship is well protected if backreaction or self-force is included. At the end, we discuss an interesting connection between Hoop Conjecture and Weak Gravity Conjecture.
Three-dimensional dilatonic gravity's rainbow: Exact solutions
International Nuclear Information System (INIS)
Hossein Hendi, Seyed; Eslam Panah, Behzad; Panahiyan, Shahram
2016-01-01
Deep relations of dark energy scenario and string theory results into dilaton gravity, on the one hand, and the connection between quantum gravity and gravity's rainbow, on the other hand, motivate us to consider three-dimensional dilatonic black hole solutions in gravity's rainbow. We obtain two classes of the solutions, which are polynomial and logarithmic forms. We also calculate conserved and thermodynamic quantities, and examine the first law of thermodynamics for both classes. In addition, we study thermal stability and show that one of the classes is thermally stable while the other one is unstable.
No hair theorem in quasi-dilaton massive gravity
Energy Technology Data Exchange (ETDEWEB)
Wu, De-Jun, E-mail: wudejun10@mails.ucas.ac.cn [School of Physics, University of Chinese Academy of Sciences, Beijing 100049 (China); Zhou, Shuang-Yong, E-mail: sxz353@case.edu [Department of Physics, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106 (United States)
2016-06-10
We investigate the static, spherically symmetric black hole solutions in the quasi-dilaton model and its generalizations, which are scalar extended dRGT massive gravity with a shift symmetry. We show that, unlike generic scalar extended massive gravity models, these theories do not admit static, spherically symmetric black hole solutions until the theory parameters in the dRGT potential are fine-tuned. When fine-tuned, the geometry of the static, spherically symmetric black hole is necessarily that of general relativity and the quasi-dilaton field is constant across the spacetime. The fine-tuning and the no hair theorem apply to black holes with flat, anti-de Sitter or de Sitter asymptotics.
No hair theorem in quasi-dilaton massive gravity
International Nuclear Information System (INIS)
Wu, De-Jun; Zhou, Shuang-Yong
2016-01-01
We investigate the static, spherically symmetric black hole solutions in the quasi-dilaton model and its generalizations, which are scalar extended dRGT massive gravity with a shift symmetry. We show that, unlike generic scalar extended massive gravity models, these theories do not admit static, spherically symmetric black hole solutions until the theory parameters in the dRGT potential are fine-tuned. When fine-tuned, the geometry of the static, spherically symmetric black hole is necessarily that of general relativity and the quasi-dilaton field is constant across the spacetime. The fine-tuning and the no hair theorem apply to black holes with flat, anti-de Sitter or de Sitter asymptotics.
Directory of Open Access Journals (Sweden)
Ran Tao
2014-01-01
Full Text Available RANS simulation is widely used in the flow prediction of centrifugal pumps. Influenced by impeller rotation and streamline curvature, the eddy viscosity models with turbulence isotropy assumption are not accurate enough. In this study, Spalart-Shur rotation/curvature correction was applied on the SST k-ω turbulence model. The comparative assessment of the correction was proceeded in the simulations of a centrifugal pump impeller. CFD results were compared with existing PIV and LDV data under the design and low flow rate off-design conditions. Results show the improvements of the simulation especially in the situation that turbulence strongly produced due to undesirable flow structures. Under the design condition, more reasonable turbulence kinetic energy contour was captured after correction. Under the low flow rate off-design condition, the prediction of turbulence kinetic energy and velocity distributions became much more accurate when using the corrected model. So, the rotation/curvature correction was proved effective in this study. And, it is also proved acceptable and recommended to use in the engineering simulations of centrifugal pump impellers.
Holographic conductivity for logarithmic charged dilaton-Lifshitz solutions
Directory of Open Access Journals (Sweden)
A. Dehyadegari
2016-07-01
Full Text Available We disclose the effects of the logarithmic nonlinear electrodynamics on the holographic conductivity of Lifshitz dilaton black holes/branes. We analyze thermodynamics of these solutions as a necessary requirement for applying gauge/gravity duality, by calculating conserved and thermodynamic quantities such as the temperature, entropy, electric potential and mass of the black holes/branes. We calculate the holographic conductivity for a (2+1-dimensional brane boundary and study its behavior in terms of the frequency per temperature. Interestingly enough, we find out that, in contrast to the Lifshitz–Maxwell-dilaton black branes which have conductivity for all z, here in the presence of nonlinear gauge field, the holographic conductivity does exist provided z≤3 and vanishes for z>3. It is shown that independent of the nonlinear parameter β, the real part of the conductivity is the same for a specific value of frequency per temperature in both AdS and Lifshitz cases. Besides, the behavior of real part of conductivity for large frequencies has a positive slope with respect to large frequencies for a system with Lifshitz symmetry whereas it tends to a constant for a system with AdS symmetry. This behavior may be interpreted as existence of an additional charge carrier rather than the AdS case, and is due to the presence of the scalar dilaton field in model. Similar behavior for optical conductivity of single-layer graphene induced by mild oxygen plasma exposure has been reported.
Black branes as piezoelectrics.
Armas, Jay; Gath, Jakob; Obers, Niels A
2012-12-14
We find a realization of linear electroelasticity theory in gravitational physics by uncovering a new response coefficient of charged black branes, exhibiting their piezoelectric behavior. Taking charged dilatonic black strings as an example and using the blackfold approach we measure their elastic and piezolectric moduli. We also use our results to draw predictions about the equilibrium condition of charged dilatonic black rings in dimensions higher than six.
Dilaton vs Higgs: Nearly Conformal Physics
Kozlov, G. A.
2016-04-01
We consider the model in which the conformal symmetry can be broken spontaneously, and a light scalar dilaton could emerge in the low-energy spectrum. The contribution of the dark photon production relevant to two photons decays of a Higgs boson/dilaton is discussed.
Classical resolution of singularities in dilaton cosmologies
Bergshoeff, EA; Collinucci, A; Roest, D; Russo, JG; Townsend, PK
2005-01-01
For models of dilaton gravity with a possible exponential potential, such as the tensor-scalar sector of ITA supergravity, we show how cosmological solutions correspond to trajectories in a 2D Milne space (parametrized by the dilaton and the scale factor). Cosmological singularities correspond to
Slowly varying dilaton cosmologies and their field theory duals
International Nuclear Information System (INIS)
Awad, Adel; Das, Sumit R.; Ghosh, Archisman; Oh, Jae-Hyuk; Trivedi, Sandip P.
2009-01-01
We consider a deformation of the AdS 5 xS 5 solution of IIB supergravity obtained by taking the boundary value of the dilaton to be time dependent. The time dependence is taken to be slowly varying on the anti-de Sitter (AdS) scale thereby introducing a small parameter ε. The boundary dilaton has a profile which asymptotes to a constant in the far past and future and attains a minimum value at intermediate times. We construct the supergravity (sugra) solution to first nontrivial order in ε, and find that it is smooth, horizon-free, and asymptotically AdS 5 xS 5 in the far future. When the intermediate values of the dilaton becomes small enough the curvature becomes of order the string scale and the sugra approximation breaks down. The resulting dynamics is analyzed in the dual SU(N) gauge theory on S 3 with a time dependent coupling constant which varies slowly. When Nε 5 xS 5 again. When Nε>>1, we formulate a classical adiabatic perturbation theory based on coherent states which arises in the large N limit. For large values of the 't Hooft coupling this reproduces the supergravity results. For small 't Hooft coupling the coherent state calculations become involved and we cannot reach a definite conclusion. We argue that the final state should have a dual description which is mostly smooth AdS 5 space with the possible presence of a small black hole.
Quantum Mechanics of Black Holes
Giddings, Steven B.
1994-01-01
These lectures give a pedagogical review of dilaton gravity, Hawking radiation, the black hole information problem, and black hole pair creation. (Lectures presented at the 1994 Trieste Summer School in High Energy Physics and Cosmology)
International Nuclear Information System (INIS)
Rami, El-nabulsi Ahmad
2010-01-01
We discuss a new class of RSII braneworld cosmology exhibiting accelerated expansion and dominated by quintessence. It is explicitly demonstrated that the universe expansion history (transition from inflation to deceleration epoch to acceleration and effective quintessence era) may naturally occur in such unified theory for some classes of inverse scalar potentials. Besides a decaying effective cosmological constant, the model incorporates an increasing black hole mass, an increasing Maxwellian electrical charge with cosmic time and a time-dependent brane tension. The cosmological model exhibits several features of cosmological and astrophysical interest for both the early and late universe consistent with recent observations, in particular the ones concerned with the gravitational constants, black holes masses and charges and variation of the gauge coupling parameters with cosmic time. One interesting mark of the constructed model concerns the fact that a black hole mass surrounded by quintessence energy may increase with time even if the horizon disappears. (general)
Testing a Dilaton Gravity Model Using Nucleosynthesis
International Nuclear Information System (INIS)
Boran, S.; Kahya, E. O.
2014-01-01
Big bang nucleosynthesis (BBN) offers one of the most strict evidences for the Λ-CDM cosmology at present, as well as the cosmic microwave background (CMB) radiation. In this work, our main aim is to present the outcomes of our calculations related to primordial abundances of light elements, in the context of higher dimensional steady-state universe model in the dilaton gravity. Our results show that abundances of light elements (primordial D, 3 He, 4 He, T, and 7 Li) are significantly different for some cases, and a comparison is given between a particular dilaton gravity model and Λ-CDM in the light of the astrophysical observations
Runaway dilaton and equivalence principle violations
Damour, Thibault Marie Alban Guillaume; Veneziano, Gabriele; Damour, Thibault; Piazza, Federico; Veneziano, Gabriele
2002-01-01
In a recently proposed scenario, where the dilaton decouples while cosmologically attracted towards infinite bare string coupling, its residual interactions can be related to the amplitude of density fluctuations generated during inflation, and are large enough to be detectable through a modest improvement on present tests of free-fall universality. Provided it has significant couplings to either dark matter or dark energy, a runaway dilaton can also induce time-variations of the natural "constants" within the reach of near-future experiments.
Thin-shell wormholes in dilaton gravity
International Nuclear Information System (INIS)
Eiroa, Ernesto F.; Simeone, Claudio
2005-01-01
In this work we construct charged thin-shell Lorentzian wormholes in dilaton gravity. The exotic matter required for the construction is localized in the shell and the energy conditions are satisfied outside the shell. The total amount of exotic matter is calculated and its dependence with the parameters of the model is analyzed
Holographic Fermions in Anisotropic Einstein-Maxwell-Dilaton-Axion Theory
International Nuclear Information System (INIS)
Kuang, Xiao-Mei; Fang, Li-Qing
2015-01-01
We investigate the properties of the holographic Fermionic system dual to an anisotropic charged black brane bulk in Einstein-Maxwell-Dilaton-Axion gravity theory. We consider the minimal coupling between the Dirac field and the gauge field in the bulk gravity theory and mainly explore the dispersion relation exponents of the Green functions of the dual Fermionic operators in the dual field theory. We find that along both the anisotropic and the isotropic directions the Fermi momentum will be effected by the anisotropy of the bulk theory. However, the anisotropy has influence on the dispersion relation which is almost linear for massless Fermions with charge q=2. The universal properties that the mass and the charge of the Fermi possibly correspond to nonlinear dispersion relation are also investigated
Thermodynamics of Einstein-Born-Infeld black holes in three dimensions
International Nuclear Information System (INIS)
Myung, Yun Soo; Kim, Yong-Wan; Park, Young-Jai
2008-01-01
We show that all thermodynamic quantities of the Einstein-Born-Infeld black holes in three dimensions can be obtained from the dilaton and its potential of two-dimensional dilaton gravity through dimensional reduction. These are all between nonrotating uncharged BTZ (Banados-Teitelboim-Zanelli) black hole (NBTZ) and charged BTZ black hole (CBTZ).
Dilaton cosmology and the modified uncertainty principle
International Nuclear Information System (INIS)
Majumder, Barun
2011-01-01
Very recently Ali et al. (2009) proposed a new generalized uncertainty principle (with a linear term in Plank length which is consistent with doubly special relativity and string theory. The classical and quantum effects of this generalized uncertainty principle (termed as modified uncertainty principle or MUP) are investigated on the phase space of a dilatonic cosmological model with an exponential dilaton potential in a flat Friedmann-Robertson-Walker background. Interestingly, as a consequence of MUP, we found that it is possible to get a late time acceleration for this model. For the quantum mechanical description in both commutative and MUP framework, we found the analytical solutions of the Wheeler-DeWitt equation for the early universe and compare our results. We have used an approximation method in the case of MUP.
Quintessence as a run-away dilaton
Gasperini, M; Veneziano, Gabriele
2002-01-01
We consider a late-time cosmological model based on a recent proposal that the infinite-bare-coupling limit of superstring/M-theory exists and has good phenomenological properties, including a vanishing cosmological constant, and a massless, decoupled dilaton. As it runs away to $+ \\infty$, the dilaton can play the role of the quintessence field recently advocated to drive the late-time accelerated expansion of the Universe. If, as suggested by some string theory examples, appreciable deviations from General Relativity persist even today in the dark matter sector, the Universe may smoothly evolve from an initial "focussing" stage, lasting till radiation-matter equality, to a "dragging" regime, which eventually gives rise to an accelerated expansion with frozen $\\Omega(\\rm{dark energy})/\\Omega(\\rm{dark matter})$.
Localization of bulk form fields on dilatonic domain walls
International Nuclear Information System (INIS)
Youm, Donam
2001-06-01
We study the localization properties of bulk form potentials on dilatonic domain walls. We find that bulk form potentials of any ranks can be localized as form potentials of the same ranks or one lower ranks, for any values of the dilaton coupling parameter. For large enough values of the dilaton coupling parameter, bulk form potentials of any ranks can be localized as form potentials of both the same ranks and one lower ranks. (author)
Dilaton, gaugino condensation and supersymmetry breaking
International Nuclear Information System (INIS)
Taylor, T.R.; Northeastern Univ., Boston, MA
1990-01-01
Non-perturbative condensation of gauginos belonging to a gauge group of the form G 1 xG 2 x...xG p , where G n are non-abelian subgroups, is examined in superstring theory by utilizing the effective lagrangian techniques. A supersymmetric vacuum with stable expectation values of the dilaton and moduli fields is shown to exist provided that the gauge group satisfies one non-trivial constraint. (orig.)
Conformal anomaly actions for dilaton interactions
Directory of Open Access Journals (Sweden)
Rose Luigi Delle
2014-01-01
Full Text Available We discuss, in conformally invariant field theories such as QCD with massless fermions, a possible link between the perturbative signature of the conformal anomaly, in the form of anomaly poles of the 1-particle irreducible effective action, and its descrip- tion in terms of Wess-Zumino actions with a dilaton. The two descriptions are expected to capture the UV and IR behaviour of the conformal anomaly, in terms of fundamental and effective degrees of freedom respectively, with the dilaton effective state appearing in a nonlinear realization. As in the chiral case, conformal anomalies seem to be related to the appearance of these effective interactions in the 1PI action in all the gauge-invariant sectors of the Standard Model. We show that, as a consequence of the underlying anomalous symmetry, the infinite hierarchy of recurrence relations involving self-interactions of the dilaton is entirely determined only by the first four of them. This relation can be generalized to any even space-time dimension.
Coupled dilaton and electromagnetic field in cylindrically symmetric ...
Indian Academy of Sciences (India)
An exact solution is obtained for coupled dilaton and electromagnetic ﬁeld in a cylindrically symmetric spacetime where an axial magnetic ﬁeld as well as a radial electric ﬁeld both are present. Depending on the choice of the arbitrary constants our solution reduces either to dilatonic gravity with pure electric ﬁeld or to that ...
The confining string from the soft dilaton theorem
International Nuclear Information System (INIS)
Alvarez, Enrique; Gomez, Cesar
2000-01-01
A candidate for the confining string of gauge theories is constructed via a representation of the ultraviolet divergences of quantum field theory by a closed string dilaton insertion, computed through the soft dilaton theorem. The resulting (critical) confining string is conformally invariant, singles out naturally d=4 dimensions, and can not be used to represent theories with Landau poles
Varying dilaton as a tracer of classical string interactions
Dodelson, Matthew; Silverstein, Eva; Torroba, Gonzalo
2017-09-01
We analyze tree-level string amplitudes in a linear dilaton background, motivated by its use as a gauge-invariant tracer of string interactions in scattering experiments and its genericity among simple perturbative string theory limits. A simple case is given by a lightlike dependence for the dilaton. The zero mode of the embedding coordinate in the direction of dilaton variation requires special care. Employing Gaussian wave packets and a well-defined modification of the dilaton profile far from the dominant interaction region, we obtain finite results which explicitly reproduce the interaction time scales expected from joining and splitting interactions involving oscillating strings in simple string scattering processes. There is an interesting interplay between the effects of the linear dilaton and the i ɛ prescription. In more general circumstances this provides a method for tracing the degree of nonlocality in string interactions, and it gives a basis for further studies of perturbative supercritical string theory at higher loop order.
Scaling solutions for dilaton quantum gravity
Energy Technology Data Exchange (ETDEWEB)
Henz, T.; Pawlowski, J.M., E-mail: j.pawlowski@thphys.uni-heidelberg.de; Wetterich, C.
2017-06-10
Scaling solutions for the effective action in dilaton quantum gravity are investigated within the functional renormalization group approach. We find numerical solutions that connect ultraviolet and infrared fixed points as the ratio between scalar field and renormalization scale k is varied. In the Einstein frame the quantum effective action corresponding to the scaling solutions becomes independent of k. The field equations derived from this effective action can be used directly for cosmology. Scale symmetry is spontaneously broken by a non-vanishing cosmological value of the scalar field. For the cosmology corresponding to our scaling solutions, inflation arises naturally. The effective cosmological constant becomes dynamical and vanishes asymptotically as time goes to infinity.
International Nuclear Information System (INIS)
Kallosh, R.
1993-01-01
In this talk some essential features of stringy black holes are described. The author considers charged U(1) and U(1) x U(1) four-dimensional axion-dilaton black holes. The Hawking temperature and the entropy of all solutions are shown to be simple functions of the squares of supercharges, defining the positivity bounds. Spherically symmetric and multi black hole solutions are presented. The extreme solutions with zero entropy (holons) represent a ground state of the theory and are characterized by elementary dilaton, axion, electric, and magnetic charges. The attractive gravitational and axion-dilaton force is balanced by the repulsive electromagnetic force. The author discusses the possibility of splitting of nearly extreme black holes. 11 refs
Signatures of Higgs dilaton and critical Higgs inflation.
García-Bellido, Juan
2018-03-06
We test the Higgs dilaton inflation model (HDM) using the latest cosmological datasets, including the cosmic microwave background temperature, polarization and lensing data from the Planck satellite (2015), the BICEP and Keck Array experiments, the type Ia supernovae from the JLA catalogue, the baryon acoustic oscillations from CMASS, LOWZ and 6dF, the weak lensing data from the CFHTLenS survey and the matter power spectrum measurements from the latest SDSS data release. We find that the values of all cosmological parameters allowed by the HDM are well within the Planck satellite (2015) constraints. In particular, we determine [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] (at 95.5% c.l.). We also place new stringent constraints on the couplings of the HDM, ξ χ Higgs inflation model, taking into account the running of both the self-coupling λ( μ ) and the non-minimal coupling to gravity ξ ( μ ). We find peaks in the curvature power spectrum at scales corresponding to the critical value μ that re-enter during the radiation era and collapse to form a broad distribution of clustered primordial black holes, which could constitute today the main component of dark matter.This article is part of the Theo Murphy meeting issue 'Higgs cosmology'. © 2018 The Author(s).
On light dilaton extensions of the Standard Model
International Nuclear Information System (INIS)
Megías, Eugenio; Pujolàs, Oriol; Quirós, Mariano
2016-01-01
We discuss the presence of a light dilaton in Conformal Field Theories deformed by a single scalar operator, in the holographic realization consisting of confining Renormalization Group flows. Then, we apply this formalism to study the extension of the Standard Model with a light dilaton in a 5D warped model. We study the spectrum of scalar and vector perturbations, compare the model predictions with Electroweak Precision Tests and find the corresponding bounds for the lightest modes. Finally, we analyze the possibility that the Higgs resonance found at the LHC be a dilaton
Charged black holes with scalar hair
Energy Technology Data Exchange (ETDEWEB)
Fan, Zhong-Ying; Lü, H. [Center for Advanced Quantum Studies, Department of Physics,Beijing Normal University, Beijing 100875 (China)
2015-09-10
We consider a class of Einstein-Maxwell-Dilaton theories, in which the dilaton coupling to the Maxwell field is not the usual single exponential function, but one with a stationary point. The theories admit two charged black holes: one is the Reissner-Nordstrøm (RN) black hole and the other has a varying dilaton. For a given charge, the new black hole in the extremal limit has the same AdS{sub 2}×Sphere near-horizon geometry as the RN black hole, but it carries larger mass. We then introduce some scalar potentials and obtain exact charged AdS black holes. We also generalize the results to black p-branes with scalar hair.
Quantum dilaton gravity in two dimensions with matter
International Nuclear Information System (INIS)
Grumiller, D.M.L.
2001-05-01
One of the main goals of 20 th century physics was the quantization of gravity. Despite of 70 years of research a comprehensive theory fulfilling this task could not be obtained. There are various explanations for this failure: gravity is a non-linear theory and as opposed to other field theories which are defined on a fixed background manifold, geometry becomes dynamical in general relativity. It is perturbatively non-renormalizable in contrast to the Standard Model of particle physics. Experimental evidence for quantum gravity is scarce due to its sheer weakness. Therefore, physicists have considered various toy models -- among them the so-called dilaton models in two dimensions -- in order to separate technical problems from conceptual ones. Unfortunately, most of them lack a certain feature present in ordinary gravity: they contain no continuous physical degrees of freedom. One way to overcome this without leaving the comfortable realm of two dimensions is the inclusion of matter. In this thesis special emphasis is put on the spherically reduced Einstein-massless-Klein-Gordon model using a first order approach for geometric quantities, because phenomenologically it is probably the most relevant of all dilaton models with matter. After a Hamiltonian BRST analysis path integral quantization is performed using temporal gauge for the Cartan variables. Retrospectively, the simpler Faddeev-Popov approach turns out to be sufficient. It is possible to eliminate all unphysical and geometric quantities establishing a non-local and non-polynomial action depending solely on the scalar field and on some integration constants, fixed by suitable boundary conditions on the asymptotic effective line element. Then, attention is turned to the evaluation of the (two) lowest order tree vertices, explicitly assuming a perturbative expansion in the scalar field being valid. Each of them diverges, but unexpected cancellations yield a finite 'S'-matrix element when both contributions
Exact solutions and critical chaos in dilaton gravity with a boundary
Energy Technology Data Exchange (ETDEWEB)
Fitkevich, Maxim [Institute for Nuclear Research of the Russian Academy of Sciences,60th October Anniversary Prospect 7a, Moscow 117312 (Russian Federation); Moscow Institute of Physics and Technology,Institutskii per. 9, Dolgoprudny 141700, Moscow Region (Russian Federation); Levkov, Dmitry [Institute for Nuclear Research of the Russian Academy of Sciences,60th October Anniversary Prospect 7a, Moscow 117312 (Russian Federation); Zenkevich, Yegor [Dipartimento di Fisica, Università di Milano-Bicocca,Piazza della Scienza 3, I-20126 Milano (Italy); INFN, sezione di Milano-Bicocca,I-20126 Milano (Italy); National Research Nuclear University MEPhI,Moscow 115409 (Russian Federation)
2017-04-19
We consider (1+1)-dimensional dilaton gravity with a reflecting dynamical boundary. The boundary cuts off the region of strong coupling and makes our model causally similar to the spherically-symmetric sector of multidimensional gravity. We demonstrate that this model is exactly solvable at the classical level and possesses an on-shell SL(2, ℝ) symmetry. After introducing general classical solution of the model, we study a large subset of soliton solutions. The latter describe reflection of matter waves off the boundary at low energies and formation of black holes at energies above critical. They can be related to the eigenstates of the auxiliary integrable system, the Gaudin spin chain. We argue that despite being exactly solvable, the model in the critical regime, i.e. at the verge of black hole formation, displays dynamical instabilities specific to chaotic systems. We believe that this model will be useful for studying black holes and gravitational scattering.
Dilaton quantum cosmology in two dimensions
International Nuclear Information System (INIS)
Mazzitelli, F.D.; Russo, J.G.
1992-11-01
We consider a renormalizable two-dimensional model of dilaton gravity coupled to a set of conformal fields as a toy model for quantum cosmology. We discuss the cosmological solutions of the model and study the effect of including the back reaction due to quantum corrections. As a result, when the matter density is below some threshold new singularities form in a weak coupling region, which suggests that they will not be removed in full quantum theory. We also solve the Wheeler-DeWitt equation. Depending on the quantum state of the Universe, the singularities may appear in a quantum region where the wave function is not oscillatory, i.e., when there is not a well defined notion of classical spacetime. (author). 29 refs, 4 figs
Very light dilaton and naturally light Higgs boson
Hong, Deog Ki
2018-02-01
We study very light dilaton, arising from a scale-invariant ultraviolet theory of the Higgs sector in the standard model of particle physics. Imposing the scale symmetry below the ultraviolet scale of the Higgs sector, we alleviate the fine-tuning problem associated with the Higgs mass. When the electroweak symmetry is spontaneously broken radiatively à la Coleman-Weinberg, the dilaton develops a vacuum expectation value away from the origin to give an extra contribution to the Higgs potential so that the Higgs mass becomes naturally around the electroweak scale. The ultraviolet scale of the Higgs sector can be therefore much higher than the electroweak scale, as the dilaton drives the Higgs mass to the electroweak scale. We also show that the light dilaton in this scenario is a good candidate for dark matter of mass m D ˜ 1 eV - 10 keV, if the ultraviolet scale is about 10-100 TeV. Finally we propose a dilaton-assisted composite Higgs model to realize our scenario. In addition to the light dilaton the model predicts a heavy U(1) axial vector boson and two massive, oppositely charged, pseudo Nambu-Goldstone bosons, which might be accessible at LHC.
Quantum scattering in two black hole moduli space
International Nuclear Information System (INIS)
Sakamoto, Kenji; Shiraishi, Kiyoshi
2003-01-01
We discuss the quantum scattering process in a moduli space consisting of two maximally charged dilaton black holes. The black hole moduli space geometry has different structures for arbitrary dimensions and various values of the dilaton coupling. We study the quantum effects of the different moduli space geometries with scattering process. Then, it is found that there is a resonance state on certain moduli spaces
International Nuclear Information System (INIS)
Destounis, Kyriakos; Panotopoulos, Grigoris; Rincon, Angel
2018-01-01
We study the stability under scalar perturbations, and we compute the quasinormal modes of the Einstein-Born-Infeld dilaton spacetime in 1 + 3 dimensions. Solving the full radial equation in terms of hypergeometric functions, we provide an exact analytical expression for the spectrum. We find that the frequencies are purely imaginary, and we confirm our results by computing them numerically. Although the scalar field that perturbs the black hole is electrically neutral, an instability similar to that seen in charged scalar perturbations of the Reissner-Nordstroem black hole is observed. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Destounis, Kyriakos; Panotopoulos, Grigoris [Universidade de Lisboa, Centro Multidisciplinar de Astrofisica, Instituto Superior Tecnico, Lisbon (Portugal); Rincon, Angel [Pontificia Universidad Catolica de Chile, Instituto de Fisica, Santiago (Chile)
2018-02-15
We study the stability under scalar perturbations, and we compute the quasinormal modes of the Einstein-Born-Infeld dilaton spacetime in 1 + 3 dimensions. Solving the full radial equation in terms of hypergeometric functions, we provide an exact analytical expression for the spectrum. We find that the frequencies are purely imaginary, and we confirm our results by computing them numerically. Although the scalar field that perturbs the black hole is electrically neutral, an instability similar to that seen in charged scalar perturbations of the Reissner-Nordstroem black hole is observed. (orig.)
Holographic Fermi and Non-Fermi Liquids with Transitions in Dilaton Gravity
Iizuka, Norihiro; Narayan, Prithvi; Trivedi, Sandip P
2012-01-01
We study the two-point function for fermionic operators in a class of strongly coupled systems using the gauge-gravity correspondence. The gravity description includes a gauge field and a dilaton which determines the gauge coupling and the potential energy. Extremal black brane solutions in this system typically have vanishing entropy. By analyzing a charged fermion in these extremal black brane backgrounds we calculate the two-point function of the corresponding boundary fermionic operator. We find that in some region of parameter space it is of Fermi liquid type. Outside this region no well-defined quasi-particles exist, with the excitations acquiring a non-vanishing width at zero frequency. At the transition, the two-point function can exhibit non-Fermi liquid behaviour.
Signatures of Higgs dilaton and critical Higgs inflation
García-Bellido, Juan
2018-01-01
We test the Higgs dilaton inflation model (HDM) using the latest cosmological datasets, including the cosmic microwave background temperature, polarization and lensing data from the Planck satellite (2015), the BICEP and Keck Array experiments, the type Ia supernovae from the JLA catalogue, the baryon acoustic oscillations from CMASS, LOWZ and 6dF, the weak lensing data from the CFHTLenS survey and the matter power spectrum measurements from the latest SDSS data release. We find that the values of all cosmological parameters allowed by the HDM are well within the Planck satellite (2015) constraints. In particular, we determine , , , and (at 95.5% c.l.). We also place new stringent constraints on the couplings of the HDM, ξχ (at 95.5% c.l.). We find that the HDM is only slightly better than the w0waCDM model, with . Given that the HDM has two fewer parameters, we find Bayesian evidence favouring the HDM over the w0waCDM model. We also study the critical Higgs inflation model, taking into account the running of both the self-coupling λ(μ) and the non-minimal coupling to gravity ξ(μ). We find peaks in the curvature power spectrum at scales corresponding to the critical value μ that re-enter during the radiation era and collapse to form a broad distribution of clustered primordial black holes, which could constitute today the main component of dark matter. This article is part of the Theo Murphy meeting issue `Higgs cosmology'.
Dilaton dynamics from production of tensionless membranes
International Nuclear Information System (INIS)
Cremonini, Sera; Watson, Scott
2006-01-01
In this paper we consider classical and quantum corrections to cosmological solutions of 11D supergravity (SUGRA) coming from dynamics of membrane states. We first consider the supermembrane spectrum following the approach of Russo and Tseytlin for consistent quantization. We calculate the production rate of Bogomol'nyi-Prasad-Sommerfield (BPS) membrane bound states in a cosmological background and find that such effects are generically suppressed by the Planck scale, as expected. However, for a modified brane spectrum possessing enhanced symmetry, production can be finite and significant. We stress that this effect could not be anticipated given only a knowledge of the low-energy effective theory. Once on shell, inclusion of these states leads to an attractive force pulling the dilaton towards a fixed point of S-duality, namely g s =1. Although the SUGRA description breaks down in this regime, inclusion of the enhanced states suggests that the center of M-theory moduli space is a dynamical attractor. Moreover, our results seem to suggest that string dynamics does indeed favor a vacuum near fixed points of duality
Thermal power terms in the Einstein-dilaton system
International Nuclear Information System (INIS)
Zuo, Fen
2014-01-01
We employ the gauge/string duality to study the thermal power terms of various thermodynamic quantities in gauge theories and the renormalized Polyakov loop above the deconfinement phase transition. We restrict ourselves to the five-dimensional Einstein gravity coupled to a single scalar, the dilaton. The asymptotic solutions of the system for a general dilaton potential are employed to study the power contributions of various quantities. If the dilaton is dual to the dimension-4 operator TrF μν 2 , no power corrections would be generated. Then the thermal quantities approach their asymptotic values much more quickly than those observed in lattice simulation. When the dimension of the dual operator is different from 4, various power terms are generated. The lowest power contributions to the thermal quantities are always quadratic in the dilaton, while that of the Polyakov loop is linear. As a result, the quadratic terms in inverse temperature for both the trace anomaly and the Polyakov loop, observed in lattice simulation, cannot be implemented consistently in the system. This is in accordance with the field theory expectation, where no gauge-invariant operator can accommodate such contributions. Two simple models, where the dilaton is dual to operators with different dimensions, are studied in detail to clarify the conclusion.
Symmetries, holography, and quantum phase transition in two-dimensional dilaton AdS gravity
Cadoni, Mariano; Ciulu, Matteo; Tuveri, Matteo
2018-05-01
We revisit the Almheiri-Polchinski dilaton gravity model from a two-dimensional (2D) bulk perspective. We describe a peculiar feature of the model, namely the pattern of conformal symmetry breaking using bulk Killing vectors, a covariant definition of mass and the flow between different vacua of the theory. We show that the effect of the symmetry breaking is both the generation of an infrared scale (a mass gap) and to make local the Goldstone modes associated with the asymptotic symmetries of the 2D spacetime. In this way a nonvanishing central charge is generated in the dual conformal theory, which accounts for the microscopic entropy of the 2D black hole. The use of covariant mass allows to compare energetically the two different vacua of the theory and to show that at zero temperature the vacuum with a constant dilaton is energetically preferred. We also translate in the bulk language several features of the dual CFT discussed by Maldacena et al. The uplifting of the 2D model to (d +2 )-dimensional theories exhibiting hyperscaling violation is briefly discussed.
Supersymmetry breaking in the linear representation of the dilaton
International Nuclear Information System (INIS)
Gaida, I.
1995-01-01
String effective theories with N=1 supersymmetry in 4 dimensions are subject of the discussion. These theories are effective in the sense, that they are low-energy limits of a given higher dimensional string theory after dimensional reduction and integrating out all heavy modes. At tree level the gauge coupling constant can be expressed by the vacuum expectation value of the dilaton superfield S:g 2 =2 -1 . Throughout this text S+ anti S will be denoted as the chiral representation of the dilaton. It has been shown that there exists a supersymmetric legendre transformation called supersymmetric duality, which transforms S+ anti S into a linear superfield L, where L will be called the linear representation of the dilaton. (orig.)
Surface geometry of 5D black holes and black rings
International Nuclear Information System (INIS)
Frolov, Valeri P.; Goswami, Rituparno
2007-01-01
We discuss geometrical properties of the horizon surface of five-dimensional rotating black holes and black rings. Geometrical invariants characterizing these 3D geometries are calculated. We obtain a global embedding of the 5D rotating black horizon surface into a flat space. We also describe the Kaluza-Klein reduction of the black ring solution (along the direction of its rotation) which, though it is nakedly singular, relates this solution to the 4D metric of a static black hole distorted by the presence of external scalar (dilaton) and vector ('electromagnetic') fields. The properties of the reduced black hole horizon and its embedding in E 3 are briefly discussed
Equivalence principle violations and couplings of a light dilaton
International Nuclear Information System (INIS)
Damour, Thibault; Donoghue, John F.
2010-01-01
We consider possible violations of the equivalence principle through the exchange of a light 'dilaton-like' scalar field. Using recent work on the quark-mass dependence of nuclear binding, we find that the dilaton-quark-mass coupling induces significant equivalence-principle-violating effects varying like the inverse cubic root of the atomic number - A -1/3 . We provide a general parametrization of the scalar couplings, but argue that two parameters are likely to dominate the equivalence-principle phenomenology. We indicate the implications of this framework for comparing the sensitivities of current and planned experimental tests of the equivalence principle.
Photoproduction of gravitons and dilatons in an external electromagnetic field
International Nuclear Information System (INIS)
Le Khac Huong; Hoang Ngoc Long.
1990-07-01
An attempt is made to present experimental predictions of the Kaluza-Klein based models. We consider the creation of gravitons and dilatons by photons in an external electromagnetic field, namely in the electric field of a flat condenser and in the static magnetic field. The relation between the cross sections of these two processes is given. A numerical evaluation shows that in the present technical scenario the creation of high frequency gravitons and dilatons may be indirectly observable. (author). 10 refs, 2 figs
Nonlinear structure formation with the environmentally dependent dilaton
International Nuclear Information System (INIS)
Brax, Philippe; Bruck, Carsten van de; Davis, Anne-Christine; Shaw, Douglas J.; Li, Baojiu
2011-01-01
We have studied the nonlinear structure formation of the environmentally dependent dilaton model using N-body simulations. We find that the mechanism of suppressing the scalar fifth force in high-density regions works very well. Within the parameter space allowed by the solar-system tests, the dilaton model predicts small deviations of the matter power spectrum and the mass function from their ΛCDM counterparts. The importance of taking full account of the nonlinearity of the model is also emphasized.
Electroweak vacuum stability in the Higgs-Dilaton theory
Energy Technology Data Exchange (ETDEWEB)
Shkerin, A. [Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL),CH-1015, Lausanne (Switzerland); Institute for Nuclear Research of the Russian Academy of Sciences,60th October Anniversary prospect 7a, 117312, Moscow (Russian Federation)
2017-05-30
We study the stability of the Electroweak (EW) vacuum in a scale-invariant extension of the Standard Model and General Relativity, known as a Higgs-Dilaton theory. The safety of the EW vacuum against possible transition towards another vacuum is a necessary condition for the model to be phenomenologically acceptable. We find that, within a wide range of parameters of the theory, the decay rate is significantly suppressed compared to that of the Standard Model. We also discuss properties of a tunneling solution that are specific to the Higgs-Dilaton theory.
Interior design of a two-dimensional semiclassical black hole
Levanony, Dana; Ori, Amos
2009-10-01
We look into the inner structure of a two-dimensional dilatonic evaporating black hole. We establish and employ the homogenous approximation for the black-hole interior. Two kinds of spacelike singularities are found inside the black hole, and their structure is investigated. We also study the evolution of spacetime from the horizon to the singularity.
Interior design of a two-dimensional semiclassical black hole
International Nuclear Information System (INIS)
Levanony, Dana; Ori, Amos
2009-01-01
We look into the inner structure of a two-dimensional dilatonic evaporating black hole. We establish and employ the homogenous approximation for the black-hole interior. Two kinds of spacelike singularities are found inside the black hole, and their structure is investigated. We also study the evolution of spacetime from the horizon to the singularity.
Energy Technology Data Exchange (ETDEWEB)
Hubeny, V.
2005-01-12
We investigate the geometry of four dimensional black hole solutions in the presence of stringy higher curvature corrections to the low energy effective action. For certain supersymmetric two charge black holes these corrections drastically alter the causal structure of the solution, converting seemingly pathological null singularities into timelike singularities hidden behind a finite area horizon. We establish, analytically and numerically, that the string-corrected two-charge black hole metric has the same Penrose diagram as the extremal four-charge black hole. The higher derivative terms lead to another dramatic effect--the gravitational force exerted by a black hole on an inertial observer is no longer purely attractive. The magnitude of this effect is related to the size of the compactification manifold.
Dilaton and second-rank tensor fields as supersymmetric compensators
International Nuclear Information System (INIS)
Nishino, Hitoshi; Rajpoot, Subhash
2007-01-01
We formulate a supersymmetric theory in which both a dilaton and a second-rank tensor play roles of compensators. The basic off-shell multiplets are a linear multiplet (B μν ,χ,φ) and a vector multiplet (A μ ,λ;C μνρ ), where φ and B μν are, respectively, a dilaton and a second-rank tensor. The third-rank tensor C μνρ in the vector multiplet is ''dual'' to the conventional D field with 0 on-shell or 1 off-shell degree of freedom. The dilaton φ is absorbed into one longitudinal component of A μ , making it massive. Initially, B μν has 1 on-shell or 3 off-shell degrees of freedom, but it is absorbed into the longitudinal components of C μνρ . Eventually, C μνρ with 0 on-shell or 1 off-shell degree of freedom acquires in total 1 on-shell or 4 off-shell degrees of freedom, turning into a propagating massive field. These basic multiplets are also coupled to chiral multiplets and a supersymmetric Dirac-Born-Infeld action. Some of these results are also reformulated in superspace. The proposed mechanism may well provide a solution to the long-standing puzzle of massless dilatons and second-rank tensors in supersymmetric models inspired by string theory
Dilaton could affect abundance of dark matter particles
2007-01-01
"The amount of dark matter left over from the early universe may be less than previously believed. new research shows that the "relic abundance" of stable dark matter particles such as the neutralino may be reduced as compared to standard cosmology theories due to the effects of the "dilaton", a particle with zero spin in the gravitational sector of strings." (1 page)
Brane solutions of gravity-dilaton-axion systems
Bergshoeff, E; Collinucci, A; Gran, U; Roest, D; Vandoren, S; Lukierski, J; Sorokin, D
2005-01-01
We consider general properties of brane solutions of gravity-dilaton-axion systems. We focus on the case of 7-branes and instantons. In both cases we show that besides the standard solutions there are new deformed solutions whose charges take value in any of the three conjugacy classes of SL(2, R).
Searching for dilaton dark matter with atomic clocks
Arvanitaki, Asimina; Huang, Junwu; Van Tilburg, Ken
2015-01-01
We propose an experiment to search for ultralight scalar dark matter (DM) with dilatonic interactions. Such couplings can arise for the dilaton as well as for moduli and axion-like particles in the presence of C P violation. Ultralight dilaton DM acts as a background field that can cause tiny but coherent oscillations in Standard Model parameters such as the fine-structure constant and the proton-electron mass ratio. These minute variations can be detected through precise frequency comparisons of atomic clocks. Our experiment extends current searches for drifts in fundamental constants to the well-motivated high-frequency regime. Our proposed setups can probe scalars lighter than 1 0-15 eV with a discovery potential of dilatonic couplings as weak as 1 0-11 times the strength of gravity, improving current equivalence principle bounds by up to 8 orders of magnitude. We point out potential 1 04 sensitivity enhancements with future optical and nuclear clocks, as well as possible signatures in gravitational-wave detectors. Finally, we discuss cosmological constraints and astrophysical hints of ultralight scalar DM, and show they are complimentary to and compatible with the parameter range accessible to our proposed laboratory experiments.
Coloured Black Holes in Higher Curvature String Gravity
Kanti, Panagiota
1997-01-01
We consider the combined Yang Mills-Dilaton-Gravity system in the presence of a Gauss-Bonnet term as it appears in the $4D$ Effective Superstring Action. We give analytical arguments and demonstrate numerically the existence of black hole solutions with non-trivial dilaton and Yang Mills hair for the particular case of SU(2) gauge fields. The thermodynamical properties of the solutions are also discussed.
On attractor mechanism of AdS4 black holes
International Nuclear Information System (INIS)
Anabalón, Andrés; Astefanesei, Dumitru
2013-01-01
We construct a general family of exact non-extremal 4-dimensional black holes in AdS gravity with U(1) gauge fields non-minimally coupled to a dilaton and a non-trivial dilaton potential. These black holes can have spherical, toroidal, and hyperbolic horizon topologies. We use the entropy function formalism to obtain the near horizon data in the extremal limit. Due to the non-trivial self-interaction of the scalar field, the zero temperature black holes can have a finite horizon area even if only the electric field is turned on
Neutron stars in screened modified gravity: Chameleon versus dilaton
Brax, Philippe; Davis, Anne-Christine; Jha, Rahul
2017-04-01
We consider the scalar field profile around relativistic compact objects such as neutron stars for a range of modified gravity models with screening mechanisms of the chameleon and Damour-Polyakov types. We focus primarily on inverse power law chameleons and the environmentally dependent dilaton as examples of both mechanisms. We discuss the modified Tolman-Oppenheimer-Volkoff equation and then implement a relaxation algorithm to solve for the scalar profiles numerically. We find that chameleons and dilatons behave in a similar manner and that there is a large degeneracy between the modified gravity parameters and the neutron star equation of state. This is exemplified by the modifications to the mass-radius relationship for a variety of model parameters.
Holographic renormalization of Einstein-Maxwell-Dilaton theories
International Nuclear Information System (INIS)
Kim, Bom Soo
2016-01-01
We generalize the boundary value problem with a mixed boundary condition that involves the gauge and scalar fields in the context of Einstein-Maxwell-Dilaton theories. In particular, the expectation value of the dual scalar operator can be a function of the expectation value of the current operator. The properties are prevalent in a fixed charge ensemble because the conserved charge is shared by both fields through the dilaton coupling, which is also responsible for non-Fermi liquid properties. We study the on-shell action and the stress energy tensor to note practical importances of the boundary value problem. In the presence of the scalar fields, physical quantities are not fully fixed due to the finite boundary terms that manifest in the massless scalar or the scalar with mass saturating the Breitenlohner-Freedman bound.
Frozen up dilaton and the GUT/Planck mass ratio
Davidson, Aharon; Ygael, Tomer
2017-09-01
By treating modulus and phase on equal footing, as prescribed by Dirac, local scale invariance can consistently accompany any Brans-Dicke ω-theory. We show that in the presence of a soft scale symmetry breaking term, the classical solution, if it exists, cannot be anything else but general relativistic. The dilaton modulus gets frozen up by the Weyl-Proca vector field, thereby constituting a gravitational quasi-Higgs mechanism. Assigning all grand unified scalars as dilatons, they enjoy Weyl universality, and upon symmetry breaking, the Planck (mass)2 becomes the sum of all their individual (VEV)2s. The emerging GUT/Planck (mass)2 ratio is thus ∼ ωgGUT2 / 4 π.
Solution of the dilaton problem in open bosonic string theories
Energy Technology Data Exchange (ETDEWEB)
Bern, Z. (Los Alamos National Lab., NM (United States)); Dunbar, D.C. (Liverpool Univ. (United Kingdom))
1991-01-01
One of the most remarkable features of string theories is that they seem to provide a framework for a consistent theory of quantum gravity which is unified with all other forces. String theories fall into the two basic, a priori equally interesting, categories of open and closed string theories. For the past five years virtually all attention has been focused on purely closed string theories even though the reincarnation of string theory began with the discovery of anomaly cancellation and finiteness in the Green-Schwarz open superstring. It is the authors' purpose in this essay to rekindle interest in open string theories as potential theories of nature, including gravity. All string theories naively contain a massless dilaton which couples with the strength of gravity in direct violation of experiment. They present a simple mechanism for giving the dilaton a mass in unoriented open bosonic string theories.
Solution of the dilaton problem in open bosonic string theories
International Nuclear Information System (INIS)
Bern, Z.; Dunbar, D.C.
1991-01-01
One of the most remarkable features of string theories is that they seem to provide a framework for a consistent theory of quantum gravity which is unified with all other forces. String theories fall into the two basic, a priori equally interesting, categories of open and closed string theories. For the past five years virtually all attention has been focused on purely closed string theories even though the reincarnation of string theory began with the discovery of anomaly cancellation and finiteness in the Green-Schwarz open superstring. It is the authors' purpose in this essay to rekindle interest in open string theories as potential theories of nature, including gravity. All string theories naively contain a massless dilaton which couples with the strength of gravity in direct violation of experiment. They present a simple mechanism for giving the dilaton a mass in unoriented open bosonic string theories
Classical and quantum integrability of 2D dilaton gravities in Euclidean space
International Nuclear Information System (INIS)
Bergamin, L; Grumiller, D; Kummer, W; Vassilevich, D V
2005-01-01
Euclidean dilaton gravity in two dimensions is studied exploiting its representation as a complexified first order gravity model. All local classical solutions are obtained. A global discussion reveals that for a given model only a restricted class of topologies is consistent with the metric and the dilaton. A particular case of string motivated Liouville gravity is studied in detail. Path integral quantization in generic Euclidean dilaton gravity is performed non-perturbatively by analogy to the Minkowskian case
Charged string solutions with dilaton and modulus fields
Cvetic, M
1994-01-01
We find charged, abelian, spherically symmetric solutions (in flat space-time) corresponding to the effective action of $D=4$ heterotic string theory with scale-dependent dilaton $\\p$ and modulus $\\vp$ fields. We take into account perturbative (genus-one), moduli-dependent `threshold' corrections to the coupling function $f(\\p,\\vp)$ in the gauge field kinetic term $f(\\p,\\vp) F^2_{\\m\
Systematic simulations of modified gravity: symmetron and dilaton models
International Nuclear Information System (INIS)
Brax, Philippe; Davis, Anne-Christine; Li, Baojiu; Winther, Hans A.; Zhao, Gong-Bo
2012-01-01
We study the linear and nonlinear structure formation in the dilaton and symmetron models of modified gravity using a generic parameterisation which describes a large class of scenarios using only a few parameters, such as the coupling between the scalar field and the matter, and the range of the scalar force on very large scales. For this we have modified the N-body simulation code ECOSMOG, which is a variant of RAMSES working in modified gravity scenarios, to perform a set of 110 simulations for different models and parameter values, including the default ΛCDM. These simulations enable us to explore a large portion of the parameter space. We have studied the effects of modified gravity on the matter power spectrum and mass function, and found a rich and interesting phenomenology where the difference with the ΛCDM template cannot be reproduced by a linear analysis even on scales as large as k ∼ 0.05 hMpc −1 . Our results show the full effect of screening on nonlinear structure formation and the associated deviation from ΛCDM. We also investigate how differences in the force mediated by the scalar field in modified gravity models lead to qualitatively different features for the nonlinear power spectrum and the halo mass function, and how varying the individual model parameters changes these observables. The differences are particularly large in the nonlinear power spectra whose shapes for f(R), dilaton and symmetron models vary greatly, and where the characteristic bump around 1 hMpc −1 of f(R) models is preserved for symmetrons, whereas an increase on much smaller scales is particular to symmetrons. No bump is present for dilatons where a flattening of the power spectrum takes place on small scales. These deviations from ΛCDM and the differences between modified gravity models, such as dilatons and symmetrons, could be tested with future surveys
Semiclassical Approach to Black Hole Evaporation
Lowe, David A.
1992-01-01
Black hole evaporation may lead to massive or massless remnants, or naked singularities. This paper investigates this process in the context of two quite different two dimensional black hole models. The first is the original CGHS model, the second is another two dimensional dilaton-gravity model, but with properties much closer to physics in the real, four dimensional, world. Numerical simulations are performed of the formation and subsequent evaporation of black holes and the results are fou...
Thermodynamical aspect of black hole solutions in heteric string theory
Fujisaki, H
2003-01-01
Thermodynamical properties of charged rotating dilatonic black holes are discussed on the basis of the general solution of Sen in the heterotic string theory compactified on a six dimensional torus. The most probable microcanonical configuration of black holes is then described in the single-massive-mode dominance scenario.
Conductivity bound from dirty black holes
Energy Technology Data Exchange (ETDEWEB)
Bitaghsir Fadafan, Kazem, E-mail: bitaghsir@shahroodut.ac.ir
2016-11-10
We propose a lower bound of the dc electrical conductivity in strongly disordered, strongly interacting quantum field theories using holography. We study linear response of black holes with broken translational symmetry in Einstein–Maxwell-dilaton theories of gravity. Using the generalized Stokes equations at the horizon, we derive the lower bound of the electrical conductivity for the dual two dimensional disordered field theory.
Standard Model-like corrections to Dilatonic Dynamics
DEFF Research Database (Denmark)
Antipin, Oleg; Krog, Jens; Mølgaard, Esben
2013-01-01
the same non-abelian global symmetries as a technicolor-like theory with matter in a complex representation of the gauge group. We then embed the electroweak gauge group within the global flavor structure and add also ordinary quark-like states to mimic the effects of the top. We find that the standard...... model-like induced corrections modify the original phase diagram and the details of the dilatonic spectrum. In particular, we show that the corrected theory exhibits near-conformal behavior for a smaller range of flavors and colors. For this range of values, however, our results suggest that near...
Dilaton gravity, Poisson sigma models and loop quantum gravity
International Nuclear Information System (INIS)
Bojowald, Martin; Reyes, Juan D
2009-01-01
Spherically symmetric gravity in Ashtekar variables coupled to Yang-Mills theory in two dimensions and its relation to dilaton gravity and Poisson sigma models are discussed. After introducing its loop quantization, quantum corrections for inverse triad components are shown to provide a consistent deformation without anomalies. The relation to Poisson sigma models provides a covariant action principle of the quantum-corrected theory with effective couplings. Results are also used to provide loop quantizations of spherically symmetric models in arbitrary D spacetime dimensions.
Quantum criticality in Einstein-Maxwell-dilaton gravity
International Nuclear Information System (INIS)
Wen, Wen-Yu
2012-01-01
We investigate the quantum Lifshitz criticality in a general background of Einstein-Maxwell-dilaton gravity. In particular, we demonstrate the existence of critical point with dynamic critical exponent z by tuning a nonminimal coupling to its critical value. We also study the effect of nonminimal coupling and exponent z to the Efimov states and holographic RG flow in the overcritical region. We have found that the nonminimal coupling increases the instability for a probe scalar to condensate and its back reaction is discussed. At last, we give a quantum mechanics treatment to a solvable system with z=2, and comment for generic z>2.
EFT for Vortices with Dilaton-dependent Localized Flux
Burgess, C P; Williams, M
2015-01-01
We study how codimension-two objects like vortices back-react gravitationally with their environment in theories (such as 4D or higher-dimensional supergravity) where the bulk is described by a dilaton-Maxwell-Einstein system. We do so both in the full theory, for which the vortex is an explicit classical `fat brane' solution, and in the effective theory of `point branes' appropriate when the vortices are much smaller than the scales of interest for their back-reaction (such as the transverse Kaluza-Klein scale). We extend the standard Nambu-Goto description to include the physics of flux-localization wherein the ambient flux of the external Maxwell field becomes partially localized to the vortex, generalizing the results of a companion paper to include dilaton-dependence for the tension and localized flux. In the effective theory, such flux-localization is described by the next-to-leading effective interaction, and the boundary conditions to which it gives rise are known to play an important role in how (and...
E-ELT constraints on runaway dilaton scenarios
Energy Technology Data Exchange (ETDEWEB)
Martinelli, M. [Institut für Theoretische Physik, Ruprecht-Karls-Universität Heidelberg, Philosophenweg 16, 69120, Heidelberg (Germany); Calabrese, E. [Sub-department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom); Martins, C.J.A.P., E-mail: m.martinelli@thphys.uni-heidelberg.de, E-mail: erminia.calabrese@physics.ox.ac.uk, E-mail: carlos.martins@astro.up.pt [Centro de Astrofìsica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal)
2015-11-01
We use a combination of simulated cosmological probes and astrophysical tests of the stability of the fine-structure constant α, as expected from the forthcoming European Extremely Large Telescope (E-ELT), to constrain the class of string-inspired runaway dilaton models of Damour, Piazza and Veneziano. We consider three different scenarios for the dark sector couplings in the model and discuss the observational differences between them. We improve previously existing analyses investigating in detail the degeneracies between the parameters ruling the coupling of the dilaton field to the other components of the universe, and studying how the constraints on these parameters change for different fiducial cosmologies. We find that if the couplings are small (e.g., α{sub b} = α{sub V} ∼ 0) these degeneracies strongly affect the constraining power of future data, while if they are sufficiently large (e.g., α{sub b} ∼> 10{sup −5}−α{sub V} ∼> 0.05, as in agreement with current constraints) the degeneracies can be partially broken. We show that E-ELT will be able to probe some of this additional parameter space.
Ruppeiner theory of black hole thermodynamics
International Nuclear Information System (INIS)
Aman, Jan E; Bedford, James; Grumiller, Daniel; Pidokrajt, Narit; Ward, John
2007-01-01
The Ruppeiner metric as determined by the Hessian of the Gibbs surface provides a geometric description of thermodynamic systems in equilibrium. An interesting example is a black hole in equilibrium with its own Hawking radiation. In this article, we present results from the Ruppeiner study of various black hole families from different gravity theories e.g. 2D dilaton gravity, BTZ, general relativity and higher-dimensional Einstein-Maxwell gravity
Violations of the equivalence principle in a dilaton-runaway scenario
Damour, Thibault Marie Alban Guillaume; Veneziano, Gabriele
2002-01-01
We explore a version of the cosmological dilaton-fixing and decoupling mechanism in which the dilaton-dependence of the low-energy effective action is extremized for infinitely large values of the bare string coupling $g_s^2 = e^{\\phi}$. We study the efficiency with which the dilaton $\\phi$ runs away towards its ``fixed point'' at infinity during a primordial inflationary stage, and thereby approximately decouples from matter. The residual dilaton couplings are found to be related to the amplitude of the density fluctuations generated during inflation. For the simplest inflationary potential, $V (\\chi) = {1/2} m_{\\chi}^2 (\\phi) \\chi^2$, the residual dilaton couplings are shown to predict violations of the universality of gravitational acceleration near the $\\Delta a / a \\sim 10^{-12}$ level. This suggests that a modest improvement in the precision of equivalence principle tests might be able to detect the effect of such a runaway dilaton. Under some assumptions about the coupling of the dilaton to dark matter...
Compact stars in alternative theories of gravity: Einstein-Dilaton-Gauss-Bonnet gravity
International Nuclear Information System (INIS)
Pani, Paolo; Berti, Emanuele; Cardoso, Vitor; Read, Jocelyn
2011-01-01
We develop a theoretical framework to study slowly rotating compact stars in a rather general class of alternative theories of gravity, with the ultimate goal of investigating constraints on alternative theories from electromagnetic and gravitational-wave observations of compact stars. Our Lagrangian includes as special cases scalar-tensor theories (and indirectly f(R) theories) as well as models with a scalar field coupled to quadratic curvature invariants. As a first application of the formalism, we discuss (for the first time in the literature) compact stars in Einstein-Dilaton-Gauss-Bonnet gravity. We show that compact objects with central densities typical of neutron stars cannot exist for certain values of the coupling constants of the theory. In fact, the existence and stability of compact stars sets more stringent constraints on the theory than the existence of black hole solutions. This work is a first step in a program to systematically rule out (possibly using Bayesian model selection) theories that are incompatible with astrophysical observations of compact stars.
Non-Kaehler heterotic string solutions with non-zero fluxes and non-constant dilaton
Energy Technology Data Exchange (ETDEWEB)
Fernández, Marisa [Universidad del País Vasco,Facultad de Ciencia y Tecnología, Departamento de Matemáticas,Apartado 644, 48080 Bilbao (Spain); Ivanov, Stefan [University of Sofia “St. Kl. Ohridski”,Faculty of Mathematics and Informatics,Blvd. James Bourchier 5, 1164 Sofia (Bulgaria); Institute of Mathematics and Informatics, Bulgarian Academy of Sciences (Bulgaria); Ugarte, Luis [Departamento de Matemáticas - I.U.M.A., Universidad de Zaragoza,Campus Plaza San Francisco, 50009 Zaragoza (Spain); Vassilev, Dimiter [Department of Mathematics and Statistics, University of New Mexico,Albuquerque, New Mexico, 87131-0001 (United States)
2014-06-12
Conformally compact and complete smooth solutions to the Strominger system with non vanishing flux, non-trivial instanton and non-constant dilaton using the first Pontrjagin form of the (−)-connection on 6-dimensional non-Kähler nilmanifold are presented. In the conformally compact case the dilaton is determined by the real slices of the elliptic Weierstrass function. The dilaton of non-compact complete solutions is given by the fundamental solution of the Laplacian on R{sup 4}. All solutions satisfy the heterotic equations of motion up to the first order of α{sup ′}.
D-brane gases and stabilization of extra dimensions in dilaton gravity
International Nuclear Information System (INIS)
Arapoglu, Savas; Kaya, Ali
2004-01-01
We consider a toy cosmological model with a gas of wrapped Dp-branes in 10-dimensional dilaton gravity compactified on a p-dimensional Ricci flat internal manifold. A consistent generalization of the low energy effective field equations in the presence of a conserved brane source coupled to dilaton is obtained. It is then shown that the compact dimensions are dynamically stabilized in string frame as a result of a balance between negative winding and positive momentum pressures. Curiously, when p=6, i.e., when the observed space is three-dimensional, the dilaton becomes a constant and stabilization in Einstein frame is also realized
On attractor mechanism of AdS{sub 4} black holes
Energy Technology Data Exchange (ETDEWEB)
Anabalón, Andrés [Departamento de Ciencias, Facultad de Artes Liberales y Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Av. Padre Hurtado 750, Viña del Mar (Chile); Université de Lyon, Laboratoire de Physique, UMR 5672, CNRS, École Normale Supérieure de Lyon, 46 allé d' Italie, F-69364 Lyon Cedex 07 (France); Astefanesei, Dumitru [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso (Chile)
2013-12-18
We construct a general family of exact non-extremal 4-dimensional black holes in AdS gravity with U(1) gauge fields non-minimally coupled to a dilaton and a non-trivial dilaton potential. These black holes can have spherical, toroidal, and hyperbolic horizon topologies. We use the entropy function formalism to obtain the near horizon data in the extremal limit. Due to the non-trivial self-interaction of the scalar field, the zero temperature black holes can have a finite horizon area even if only the electric field is turned on.
arXiv Clockwork / Linear Dilaton: Structure and Phenomenology
Giudice, Gian F.; McCullough, Matthew; Torre, Riccardo; Urbano, Alfredo
2018-06-01
The linear dilaton geometry in five dimensions, rediscovered recently in the continuum limit of the clockwork model, may offer a solution to the hierarchy problem which is qualitatively different from other extra-dimensional scenarios and leads to distinctive signatures at the LHC. We discuss the structure of the theory, in particular aspects of naturalness and UV completion, and then explore its phenomenology, suggesting novel strategies for experimental searches. In particular, we propose to analyze the diphoton and dilepton invariant mass spectra in Fourier space in order to identify an approximately periodic structure of resonant peaks. Among other signals, we highlight displaced decays from resonantly-produced long-lived states and high-multiplicity final states from cascade decays of excited gravitons.
Saddle point solutions in Yang-Mills-dilaton theory
International Nuclear Information System (INIS)
Bizon, P.
1992-01-01
The coupling of a dilaton to the SU(2)-Yang-Mills field leads to interesting non-perturbative static spherically symmetric solutions which are studied by mixed analytical and numerical methods. In the abelian sector of the theory there are finite-energy magnetic and electric monopole solutions which saturate the Bogomol'nyi bound. In the nonabelian sector there exist a countable family of globally regular solutions which are purely magnetic but have zero Yang-Mills magnetic charge. Their discrete spectrum of energies is bounded from above by the energy of the abelian magnetic monopole with unit magnetic charge. The stability analysis demonstrates that the solutions are saddle points of the energy functional with increasing number of unstable modes. The existence and instability of these solutions are 'explained' by the Morse-theory argument recently proposed by Sudarsky and Wald. (author)
Axion-dilaton domain walls and fake supergravity
International Nuclear Information System (INIS)
Sonner, Julian; Townsend, Paul K
2007-01-01
Dynamical systems methods are used to investigate domain-wall solutions of a two-parameter family of models in which gravity is coupled to an axion and to a dilaton with an exponential potential of either sign. A complete global analysis is presented for (i) constant axion and (ii) flat walls, including a study of bifurcations and a new exact domain-wall solution with non-constant axion. We reconsider 'fake-supergravity' issues in light of these results. We show, by example, how domain walls determine multi-valued superpotentials that branch at stationary points that are not stationary points of the potential, and we apply this result to potentials with anti-de Sitter vacua. We also show by example that 'adapted' truncation to a single-scalar model may be inconsistent, and we propose a 'generalized' fake-supergravity formalism that applies in some such cases
Starobinsky-Like Inflation in Dilaton-Brane Cosmology
Ellis, John; Nanopoulos, Dimitri V
2014-01-01
We discuss how Starobinsky-like inflation may emerge from dilaton dynamics in brane cosmology scenarios based on string theory, in which our universe is represented as a three-brane. The effective potential may acquire a constant term from a density of effectively point-like non-pertubative defects on the brane. Higher-genus corrections generate corrections to the effective potential that are exponentially damped at large field values, as in the Starobinsky model, but at a faster rate, leading to a smaller prediction for the tensor-to scalar perturbation ratio r. This may be compensated partially by logarithmic deformations on the world-sheet due to recoil of the defects due to scattering by string matter on the brane, which tend to enhance the tensor-to-scalar ratio.
EFT for vortices with dilaton-dependent localized flux
Energy Technology Data Exchange (ETDEWEB)
Burgess, C.P. [Physics & Astronomy, McMaster University, Hamilton, ON, L8S 4M1 (Canada); Perimeter Institute for Theoretical Physics, Waterloo, ON, N2L 2Y5 (Canada); Division PH -TH, CERN, CH-1211, Genève 23 (Switzerland); Diener, Ross [Physics & Astronomy, McMaster University, Hamilton, ON, L8S 4M1 (Canada); Perimeter Institute for Theoretical Physics, Waterloo, ON, N2L 2Y5 (Canada); Williams, M. [Instituut voor Theoretische Fysica, Katholieke Universiteit Leuven, B-3001 Leuven (Belgium)
2015-11-09
We study how codimension-two objects like vortices back-react gravitationally with their environment in theories (such as 4D or higher-dimensional supergravity) where the bulk is described by a dilaton-Maxwell-Einstein system. We do so both in the full theory, for which the vortex is an explicit classical ‘fat brane’ solution, and in the effective theory of ‘point branes’ appropriate when the vortices are much smaller than the scales of interest for their back-reaction (such as the transverse Kaluza-Klein scale). We extend the standard Nambu-Goto description to include the physics of flux-localization wherein the ambient flux of the external Maxwell field becomes partially localized to the vortex, generalizing the results of a companion paper http://arxiv.org/abs/1506.08095 to include dilaton-dependence for the tension and localized flux. In the effective theory, such flux-localization is described by the next-to-leading effective interaction, and the boundary conditions to which it gives rise are known to play an important role in how (and whether) the vortex causes supersymmetry to break in the bulk. We track how both tension and localized flux determine the curvature of the space-filling dimensions. Our calculations provide the tools required for computing how scale-breaking vortex interactions can stabilize the extra-dimensional size by lifting the dilaton’s flat direction. For small vortices we derive a simple relation between the near-vortex boundary conditions of bulk fields as a function of the tension and localized flux in the vortex action that provides the most efficient means for calculating how physical vortices mutually interact without requiring a complete construction of their internal structure. In passing we show why a common procedure for doing so using a δ-function can lead to incorrect results. Our procedures generalize straightforwardly to general co-dimension objects.
EFT for vortices with dilaton-dependent localized flux
International Nuclear Information System (INIS)
Burgess, C.P.; Diener, Ross; Williams, M.
2015-01-01
We study how codimension-two objects like vortices back-react gravitationally with their environment in theories (such as 4D or higher-dimensional supergravity) where the bulk is described by a dilaton-Maxwell-Einstein system. We do so both in the full theory, for which the vortex is an explicit classical ‘fat brane’ solution, and in the effective theory of ‘point branes’ appropriate when the vortices are much smaller than the scales of interest for their back-reaction (such as the transverse Kaluza-Klein scale). We extend the standard Nambu-Goto description to include the physics of flux-localization wherein the ambient flux of the external Maxwell field becomes partially localized to the vortex, generalizing the results of a companion paper http://arxiv.org/abs/1506.08095 to include dilaton-dependence for the tension and localized flux. In the effective theory, such flux-localization is described by the next-to-leading effective interaction, and the boundary conditions to which it gives rise are known to play an important role in how (and whether) the vortex causes supersymmetry to break in the bulk. We track how both tension and localized flux determine the curvature of the space-filling dimensions. Our calculations provide the tools required for computing how scale-breaking vortex interactions can stabilize the extra-dimensional size by lifting the dilaton’s flat direction. For small vortices we derive a simple relation between the near-vortex boundary conditions of bulk fields as a function of the tension and localized flux in the vortex action that provides the most efficient means for calculating how physical vortices mutually interact without requiring a complete construction of their internal structure. In passing we show why a common procedure for doing so using a δ-function can lead to incorrect results. Our procedures generalize straightforwardly to general co-dimension objects.
Dirac particle tunneling from black rings
International Nuclear Information System (INIS)
Jiang Qingquan
2008-01-01
Recent research shows that Hawking radiation can be treated as a quantum tunneling process, and Hawking temperatures of Dirac particles across the horizon of a black hole can be correctly recovered via the fermion tunneling method. In this paper, motivated by the fermion tunneling method, we attempt to apply the analysis to derive Hawking radiation of Dirac particles via tunneling from black ring solutions of 5-dimensional Einstein-Maxwell-dilaton gravity theory. Finally, it is interesting to find that, as in the black hole case, fermion tunneling can also result in correct Hawking temperatures for the rotating neutral, dipole, and charged black rings.
Dilaton thin-shell wormholes supported by a generalized Chaplygin gas
International Nuclear Information System (INIS)
Bejarano, Cecilia; Eiroa, Ernesto F.
2011-01-01
In this article, we construct spherical thin-shell wormholes with charge in dilaton gravity. The exotic matter required for the construction is provided by a generalized Chaplygin gas. We study the stability under perturbations preserving the symmetry. We find that the increase of the coupling between the dilaton and the electromagnetic fields reduces the range of the parameters for which stable configurations are possible.
All or nothing: On the small fluctuations of two-dimensional string theoretic black holes
Energy Technology Data Exchange (ETDEWEB)
Gilbert, Gerald [Univ. of Maryland, College Park, MD (United States); Raiten, Eric [Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
1992-10-01
A comprehensive analysis of small fluctuations about two-dimensional string-theoretic and string-inspired black holes is presented. It is shown with specific examples that two-dimensional black holes behave in a radically different way from all known black holes in four dimensions. For both the SL(2,R)/U(1) black hole and the two-dimensional black hole coupled to a massive dilaton with constant field strength, it is shown that there are a {\\it continuous infinity} of solutions to the linearized equations of motion, which are such that it is impossible to ascertain the classical linear response. It is further shown that the two-dimensional black hole coupled to a massive, linear dilaton admits {\\it no small fluctuations at all}. We discuss possible implications of our results for the Callan-Giddings-Harvey-Strominger black hole.
Astrophysical black holes in screened modified gravity
International Nuclear Information System (INIS)
Davis, Anne-Christine; Jha, Rahul; Muir, Jessica; Gregory, Ruth
2014-01-01
Chameleon, environmentally dependent dilaton, and symmetron gravity are three models of modified gravity in which the effects of the additional scalar degree of freedom are screened in dense environments. They have been extensively studied in laboratory, cosmological, and astrophysical contexts. In this paper, we present a preliminary investigation into whether additional constraints can be provided by studying these scalar fields around black holes. By looking at the properties of a static, spherically symmetric black hole, we find that the presence of a non-uniform matter distribution induces a non-constant scalar profile in chameleon and dilaton, but not necessarily symmetron gravity. An order of magnitude estimate shows that the effects of these profiles on in-falling test particles will be sub-leading compared to gravitational waves and hence observationally challenging to detect
Astrophysical black holes in screened modified gravity
Energy Technology Data Exchange (ETDEWEB)
Davis, Anne-Christine; Jha, Rahul; Muir, Jessica [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom); Gregory, Ruth, E-mail: acd@damtp.cam.ac.uk, E-mail: r.a.w.gregory@durham.ac.uk, E-mail: r.jha@damtp.cam.ac.uk, E-mail: jlmuir@umich.edu [Centre for Particle Theory, South Road, Durham, DH1 3LE (United Kingdom)
2014-08-01
Chameleon, environmentally dependent dilaton, and symmetron gravity are three models of modified gravity in which the effects of the additional scalar degree of freedom are screened in dense environments. They have been extensively studied in laboratory, cosmological, and astrophysical contexts. In this paper, we present a preliminary investigation into whether additional constraints can be provided by studying these scalar fields around black holes. By looking at the properties of a static, spherically symmetric black hole, we find that the presence of a non-uniform matter distribution induces a non-constant scalar profile in chameleon and dilaton, but not necessarily symmetron gravity. An order of magnitude estimate shows that the effects of these profiles on in-falling test particles will be sub-leading compared to gravitational waves and hence observationally challenging to detect.
Black hole entropy, universality, and horizon constraints
International Nuclear Information System (INIS)
Carlip, Steven
2006-01-01
To ask a question about a black hole in quantum gravity, one must restrict initial or boundary data to ensure that a black hole is actually present. For two-dimensional dilaton gravity, and probably a much wider class of theories, I show that the imposition of a 'stretched horizon' constraint modifies the algebra of symmetries at the horizon, allowing the use of conformal field theory techniques to determine the asymptotic density of states. The result reproduces the Bekenstein-Hawking entropy without any need for detailed assumptions about the microscopic theory. Horizon symmetries may thus offer an answer to the problem of universality of black hole entropy
Black hole entropy, universality, and horizon constraints
Energy Technology Data Exchange (ETDEWEB)
Carlip, Steven [Department of Physics, University of California, Davis, CA 95616 (United States)
2006-03-01
To ask a question about a black hole in quantum gravity, one must restrict initial or boundary data to ensure that a black hole is actually present. For two-dimensional dilaton gravity, and probably a much wider class of theories, I show that the imposition of a 'stretched horizon' constraint modifies the algebra of symmetries at the horizon, allowing the use of conformal field theory techniques to determine the asymptotic density of states. The result reproduces the Bekenstein-Hawking entropy without any need for detailed assumptions about the microscopic theory. Horizon symmetries may thus offer an answer to the problem of universality of black hole entropy.
Semiclassical approach to black hole evaporation
International Nuclear Information System (INIS)
Lowe, D.A.
1993-01-01
Black hole evaporation may lead to massive or massless remnants, or naked singularities. This paper investigates this process in the context of two quite different two-dimensional black hole models. The first is the original Callan-Giddings-Harvey-Strominger (CGHS) model, the second is another two-dimensional dilaton-gravity model, but with properties much closer to physics in the real, four-dimensional, world. Numerical simulations are performed of the formation and subsequent evaporation of black holes and the results are found to agree qualitatively with the exactly solved modified CGHS models, namely, that the semiclassical approximation breaks down just before a naked singularity appears
Hydrodynamics and Elasticity of Charged Black Branes
DEFF Research Database (Denmark)
Gath, Jakob
We consider long-wavelength perturbations of charged black branes to first order in a uidelastic derivative expansion. At first order the perturbations decouple and we treat the hydrodynamic and elastic perturbations separately. To put the results in a broader perspective, we present the rst...... as a seed solution, we obtain a class of charged black brane geometries carrying smeared Maxwell charge in Einstein-Maxwell-dilaton theory. In the specific case of ten-dimensional space-time we furthermore use T-duality to generate bent black branes with higher-form charge, including smeared D...
Phantom-like behaviour in dilatonic brane-world scenario with induced gravity
International Nuclear Information System (INIS)
Bouhmadi-Lopez, Mariam
2008-01-01
The Dvali, Gabadadze and Porrati (DGP) model has a self-accelerating solution, the positive branch, where the brane is asymptotically de Sitter. A de Sitter space-time can be seen as a boundary between quintessence-like behaviour and phantom-like behaviour. We show that in a 5D dilatonic bulk, where the dilaton has an exponential potential, with an induced gravity term on the brane, whose matter content corresponds only to vacuum energy, the positive branch solution undergoes a phantom-like stage where it faces a curvature singularity in its infinite future. The singularity can be interpreted as the 'big rip' singularity pushed towards an infinite future cosmic time. The phantom-like behaviour on the brane occurs without violating the null energy condition. There is another solution, the negative branch, where the brane can undergo an early-epoch (transient) inflationary phase induced by the dilaton field
Constraint Lie algebra and local physical Hamiltonian for a generic 2D dilatonic model
International Nuclear Information System (INIS)
Corichi, Alejandro; Karami, Asieh; Rastgoo, Saeed; Vukašinac, Tatjana
2016-01-01
We consider a class of two-dimensional dilatonic models, and revisit them from the perspective of a new set of ‘polar type’ variables. These are motivated by recently defined variables within the spherically symmetric sector of 4D general relativity. We show that for a large class of dilatonic models, including the case with matter, one can perform a series of canonical transformations in such a way that the Poisson algebra of the constraints becomes a Lie algebra. Furthermore, we construct Dirac observables and a reduced Hamiltonian that accounts for the time evolution of the system. (paper)
The twelve-flavor β-function and dilaton tests of the sextet scalar
Directory of Open Access Journals (Sweden)
Fodor Zoltan
2018-01-01
Full Text Available We discuss near-conformal gauge theories beyond the standard model (BSM where interesting results on the twelve-flavor β-function of massless fermions in the fundamental representation of the SU(3 color gauge group and dilaton tests of the light scalar with two massless fermions in the two-index symmetric tensor (sextet representation can be viewed as parts of the same BSM paradigm under investigation. The clear trend in the decreasing size of β-functions at fixed renormalized gauge coupling is interpreted as a first indicator how the conformal window (CW is approached in correlation with emergent near-conformal light scalars. BSM model building close to the CW will be influenced by differing expectations on the properties of the emergent light 0++ scalar either as a σ-particle of chiral symmetry breaking (ΧS B, or as a dilaton of scale symmetry breaking. The twelve-flavor β-function emerges as closest to the CW, perhaps near-conformal, or perhaps with an infrared fixed point (IRFP at some unexplored strong coupling inside the CW. It is premature to speculate on dilaton properties of the twelveflavor model since the near-conformal realization remains an open question. However, it is interesting and important to investigate dilaton tests of the light sextet scalar whose β-function is closest to the CW in the symmetry breaking phase and emerges as the leading candidate for dilaton tests of the light scalar. We report results from high precision analysis of the twelve-flavor β-function [1] refuting its published IRFP [2, 3]. We present our objections to recent claims [4, 5] for non-universal behavior of staggered fermions used in our analysis. We also report our first analysis of dilaton tests of the light 0++ scalar in the sextet model and comment on related post-conference developments. The dilaton test is the main thrust of this conference contribution including presentation #405 on the nf = 12 β-function and presentation #260 on dilaton
String-coupling constant and dilaton vacuum expectation value in string field theory
International Nuclear Information System (INIS)
Yoneya, Tamiaki
1987-01-01
In the first quantized approaches to strings, it is well known that the string-coupling constant is determined by the vacuum expectation value of the dilaton field. This property, however, has never been demonstrated within the framework of string field theory. An explicit reparametrization of the string field associated with the shifts of the dilaton vacuum expectation value and the string-coupling constant is constructed exhibiting the above property in the light-cone field theory of the closed bosonic string. (orig.)
Black rings and the physical process version of the first law of thermodynamics
International Nuclear Information System (INIS)
Rogatko, Marek
2005-01-01
We consider the problem of the physical process version of the first law of black ring thermodynamics in n-dimensional Einstein gravity with additional (p+1)-form field strength and dilaton fields. The first order variations of mass, angular momentum and local charge for black ring are derived. From them we prove the physical process version of the first law of thermodynamic for stationary black rings
Matter with dilaton charge in Weyl-Cartan spacetime and evolution of the universe
International Nuclear Information System (INIS)
Babourova, Olga V; Frolov, Boris N
2003-01-01
The perfect dilaton-spin fluid (as a model of the dilaton matter, the particles of which are endowed with intrinsic spin and dilaton charge) is considered as the source of the gravitational field in a Weyl-Cartan spacetime. The variational formalism of the gravitational field in a Weyl-Cartan spacetime is developed in the exterior form language. A homogeneous and isotropic universe filled with the dilaton matter as the dark matter is considered and one of the field equations is represented as the Einstein-like equation which leads to the modified Friedmann-Lemaitre equation. From this equation the absence of the initial singularity in the cosmological solution follows. Also the existence of two points of inflection of the scale factor function is established, the first of which corresponds to the early stage of the universe and the second to the modern era when the expansion with deceleration is replaced by the expansion with acceleration. Possible equations of state for the self-interacting cold dark matter are found on the basis of the modern observational data. An inflation-like solution is obtained
Conformal field theory with two kinds of Bosonic fields and two linear dilatons
International Nuclear Information System (INIS)
Kamani, Davoud
2010-01-01
We consider a two-dimensional conformal field theory which contains two kinds of the bosonic degrees of freedom. Two linear dilaton fields enable to study a more general case. Various properties of the model such as OPEs, central charge, conformal properties of the fields and associated algebras will be studied. (author)
Small dark energy and stable vacuum from Dilaton-Gauss-Bonnet coupling in TMT
Energy Technology Data Exchange (ETDEWEB)
Guendelman, Eduardo I. [Ben-Gurion University of the Negev, Department of Physics, Beer-Sheva (Israel); Nishino, Hitoshi; Rajpoot, Subhash [California State University at Long Beach, Long Beach, CA (United States)
2017-04-15
In two measures theories (TMT), in addition to the Riemannian measure of integration, being the square root of the determinant of the metric, we introduce a metric-independent density Φ in four dimensions defined in terms of scalars φ{sub a} by Φ = ε{sup μνρσ} ε{sub abcd}(∂{sub μ}φ{sub a})(∂{sub ν}φ{sub b})(∂{sub ρ}φ{sub c})(∂{sub σ}φ{sub d}). With the help of a dilaton field φ we construct theories that are globally scale invariant. In particular, by introducing couplings of the dilaton φ to the Gauss-Bonnet (GB) topological density √(-g)φ (R{sub μνρσ}{sup 2} - 4R{sub μν}{sup 2} + R{sup 2}) we obtain a theory that is scale invariant up to a total divergence. Integration of the φ{sub a} field equation leads to an integration constant that breaks the global scale symmetry. We discuss the stabilizing effects of the coupling of the dilaton to the GB-topological density on the vacua with a very small cosmological constant and the resolution of the 'TMT Vacuum-Manifold Problem' which exists in the zero cosmological-constant vacuum limit. This problem generically arises from an effective potential that is a perfect square, and it gives rise to a vacuum manifold instead of a unique vacuum solution in the presence of many different scalars, like the dilaton, the Higgs, etc. In the non-zero cosmological-constant case this problem disappears. Furthermore, the GB coupling to the dilaton eliminates flat directions in the effective potential, and it totally lifts the vacuum-manifold degeneracy. (orig.)
Instability of black holes with a Gauss-Bonnet term
International Nuclear Information System (INIS)
Ahn, Wha-Keun; Gwak, Bogeun; Lee, Wonwoo; Lee, Bum-Hoon
2015-01-01
We investigate the fragmentation instability of hairy black holes in the theory with a Gauss-Bonnet (GB) term in asymptotically flat spacetime. Our approach is through the non-perturbative fragmentation instability. By this approach, we investigate whether the initial black hole can be broken into two black holes by comparing the entropy of the initial black hole with the sum of those of two fragmented black holes. The relation between the black hole instability and the GB coupling with dilaton hair are presented. We describe the phase diagrams with respect to the mass of the black hole solutions and coupling constants. We find that a perturbatively stable black hole can be unstable under fragmentation. (orig.)
STU black holes and string triality
International Nuclear Information System (INIS)
Behrndt, K.; Kallosh, R.; Rahmfeld, J.; Shmakova, M.; Wong, W.K.
1996-01-01
We find double-extreme black holes associated with the special geometry of the Calabi-Yau moduli space with the prepotential F=STU. The area formula is STU-moduli independent and has [SL(2,Z)] 3 symmetry in space of charges. The dual version of this theory without a prepotential treats the dilaton S asymmetric vs T,U moduli. We display the dual relation between new (STU) black holes and stringy (S|TU) black holes using a particular Sp(8,Z) transformation. The area formula of one theory equals that of the dual theory when expressed in terms of dual charges. We analyze the relation between (STU) black holes to string triality of black holes: (S|TU), (T|US), (U|ST) solutions. In the democratic STU-symmetric version we find that all three S, T, and U duality symmetries are nonperturbative and mix electric and magnetic charges. copyright 1996 The American Physical Society
STU Black Holes and String Triality
Energy Technology Data Exchange (ETDEWEB)
Shmakova, Marina
2003-05-23
We found double-extreme black holes associated with the special geometry of the Calabi-Yau moduli space with the prepotential F = STU. The area formula is STU-moduli independent and has [SL(2, Z)]{sup 3} symmetry in space of charges. The dual version of this theory without prepotential treats the dilaton S asymmetric versus T,U-moduli. We display the dual relation between new (STU) black holes and stringy (S|TU) black holes using particular Sp(8,Z) transformation. The area formula of one theory equals the area formula of the dual theory when expressed in terms of dual charges. We analyze the relation between (STU) black holes to string triality of black holes: (S|TU), (T|US), (U|ST) solutions. In democratic STU-symmetric version we find that all three S and T and U duality symmetries are non-perturbative and mix electric and magnetic charges.
Dynamical black holes in low-energy string theory
Energy Technology Data Exchange (ETDEWEB)
Aniceto, Pedro [Departamento de Matemática, Instituto Superior Técnico, Universidade de Lisboa,Avenida Rovisco Pais 1, 1049 Lisboa (Portugal); Rocha, Jorge V. [Departament de Física Quàntica i Astrofísica, Institut de Ciències del Cosmos (ICCUB),Universitat de Barcelona,Martí i Franquès 1, E-08028 Barcelona (Spain)
2017-05-08
We investigate time-dependent spherically symmetric solutions of the four-dimensional Einstein-Maxwell-axion-dilaton system, with the dilaton coupling that occurs in low-energy effective heterotic string theory. A class of dilaton-electrovacuum radiating solutions with a trivial axion, previously found by Güven and Yörük, is re-derived in a simpler manner and its causal structure is clarified. It is shown that such dynamical spacetimes featuring apparent horizons do not possess a regular light-like past null infinity or future null infinity, depending on whether they are radiating or accreting. These solutions are then extended in two ways. First we consider a Vaidya-like generalisation, which introduces a null dust source. Such spacetimes are used to test the status of cosmic censorship in the context of low-energy string theory. We prove that — within this family of solutions — regular black holes cannot evolve into naked singularities by accreting null dust, unless standard energy conditions are violated. Secondly, we employ S-duality to derive new time-dependent dyon solutions with a nontrivial axion turned on. Although they share the same causal structure as their Einstein-Maxwell-dilaton counterparts, these solutions possess both electric and magnetic charges.
Abbott-Deser-Tekin Charge of Dilaton Black Holes with Squashed Horizons
Peng, Jun-Jin; Xiang, Wen-Chang; Cai, Shao-Hong
2016-08-01
Not Available Supported by the National Natural Science Foundation of China under Grant Nos 11275157 and 11505036, the Doctoral Research Fund of Guizhou Normal University in 2014, the Technology Department of Guizhou Province Fund under Grant No [2015]2114, and the Science and Technology Innovation Talent Team of Guizhou Province under Grant No (2015)4015.
Unlocking the axion-dilaton in 5D supergravity
Czech Academy of Sciences Publication Activity Database
Raeymaekers, Joris; Van den Bleeken, D.
2014-01-01
Roč. 11, Nov (2014), s. 1-54 ISSN 1029-8479 R&D Projects: GA ČR(CZ) GA14-31689S Institutional support: RVO:68378271 Keywords : supergravity models * d-branes * m-theory * black holes in string theory Subject RIV: BE - Theoretical Physics Impact factor: 6.111, year: 2014 http://link.springer.com/article/10.1007%2FJHEP11%282014%29029
Quasilocal energy, Komar charge and horizon for regular black holes
International Nuclear Information System (INIS)
Balart, Leonardo
2010-01-01
We study the Brown-York quasilocal energy for regular black holes. We also express the identity that relates the difference of the Brown-York quasilocal energy and the Komar charge at the horizon to the total energy of the spacetime for static and spherically symmetric black hole solutions in a convenient way which permits us to understand why this identity is not satisfied when we consider nonlinear electrodynamics. However, we give a relation between quantities evaluated at the horizon and at infinity when nonlinear electrodynamics is considered. Similar relations are obtained for more general static and spherically symmetric black hole solutions which include solutions of dilaton gravity theories.
History of cosmic evolution with modified Gauss-Bonnet-dilatonic coupled term
International Nuclear Information System (INIS)
Debnath, Subhra; Sanyal, Abhik Kumar; Ruz, Soumendra Nath; Mandal, Ranajit
2017-01-01
Gauss-Bonnet-dilatonic coupling in four dimensions plays an important role to explain late-time cosmic evolution. However, this term is an outcome of the low energy string effective action and thus ought to be important in the early universe too. Unfortunately, a phase-space formulation of such a theory does not exist in the literature due to branching. We therefore consider a modified theory of gravity, which contains a nonminimally coupled scalar-tensor sector in addition to a higher-order scalar curvature invariant term with Gauss-Bonnet-dilatonic coupling. Such an action unifies early inflation with late-time cosmic acceleration. The quantum version of the theory is also well behaved. (orig.)
History of cosmic evolution with modified Gauss-Bonnet-dilatonic coupled term
Energy Technology Data Exchange (ETDEWEB)
Debnath, Subhra; Sanyal, Abhik Kumar [Jangipur College, Department of Physics, Murshidabad (India); Ruz, Soumendra Nath [Ramananda Centenary College, Department of Physics, Purulia (India); Mandal, Ranajit [University of Kalyani, Department of Physics, Nadia (India)
2017-05-15
Gauss-Bonnet-dilatonic coupling in four dimensions plays an important role to explain late-time cosmic evolution. However, this term is an outcome of the low energy string effective action and thus ought to be important in the early universe too. Unfortunately, a phase-space formulation of such a theory does not exist in the literature due to branching. We therefore consider a modified theory of gravity, which contains a nonminimally coupled scalar-tensor sector in addition to a higher-order scalar curvature invariant term with Gauss-Bonnet-dilatonic coupling. Such an action unifies early inflation with late-time cosmic acceleration. The quantum version of the theory is also well behaved. (orig.)
Subsubleading soft theorems of gravitons and dilatons in the bosonic string
International Nuclear Information System (INIS)
Vecchia, Paolo Di; Marotta, Raffaele; Mojaza, Matin
2016-01-01
Starting from the amplitude with an arbitrary number of massless closed states of the bosonic string, we compute the soft limit when one of the states becomes soft to subsubleading order in the soft momentum expansion, and we show that when the soft state is a graviton or a dilaton, the full string amplitude can be expressed as a soft theorem through subsubleading order. It turns out that there are string corrections to the field theoretical limit in the case of a soft graviton, while for a soft dilaton the string corrections vanish. We then show that the new soft theorems, including the string corrections, can be simply obtained from the exchange diagrams where the soft state is attached to the other external states through the three-point string vertex of three massless states. In the soft-limit, the propagator of the exchanged state is divergent, and at tree-level these are the only divergent contributions to the full amplitude. However, they do not form a gauge invariant subset and must be supplemented with extra non-singular terms. The requirement of gauge invariance then fixes the complete amplitude through subsubleading order in the soft expansion, reproducing exactly what one gets from the explicit calculation in string theory. From this it is seen that the string corrections at subsubleading order arise as a consequence of the three-point amplitude having string corrections in the bosonic string. When specialized to a soft dilaton, it remarkably turns out that the string corrections vanish and that the non-singular piece of the subsubleading term of the dilaton soft theorem is the generator of space-time special conformal transformation.
Proton and neutron charge form factors in soliton model with dilaton-quarkonium fields
International Nuclear Information System (INIS)
Magar, E.N.; Nikolaev, V.A.; Tkachev, O.G.; Novozhilov, V.Yu.
1997-01-01
Nucleon electromagnetic form factors are considered in the framework of the generalized Skyrme model with dilaton-quarkonium fields. In our first publication we got big discrepancy between calculated form factors and dipole approximation formula. Here we have reasonably good accordance between them in finite impulse region after vector meson dominance has been taken into account. Omega- and rho-mesons have been included only into hadron structure of the photon
S- and T-self-dualities in dilatonic f(R) theories
Energy Technology Data Exchange (ETDEWEB)
Rador, Tonguc [Bogazici University, Department of Physics, Istanbul (Turkey); Izmir Institute of Technology, Department of Physics, Izmir (Turkey)
2017-12-15
We search for theories, in general spacetime dimensions, that would incorporate a dilaton and higher powers of the scalar Ricci curvature such that they have exact S- or T-self-dualities. The theories we find are free of Ostrogradsky instabilities. We also show that within the framework we are confining ourselves, a theory of the form mentioned above cannot have both T- and S-dualities except for the case where the action is linear in the scalar curvature. (orig.)
Black holes and gravitating axially symmetric non-abelian solitons in d 3+1 and d = 4+1
International Nuclear Information System (INIS)
Radu, Eugen; Shnir, Yasha; Tchrakian, D. H.
2010-01-01
We construct static, asymptotically flat solutions of SU(2) Einstein-Yang-Mills (EYM) theory in 4+1 dimensions, subject to bi-azimuthal symmetry. The results are compared with similar solutions of the SU(2) Yang--Mills--dilaton (YMd) model. Both particle-like and black hole solutions are considered.
Rizwan, C. L. Ahmed; Vaid, Deepak
2018-05-01
We study holographic superconductivity in low-energy stringy Garfinkle-Horowitz-Strominger (GHS) dilaton black hole background. We finds that superconducting properties are much similar to s-wave superconductors. We show that the second-order phase transition indicated from thermodynamic geometry is not different from superconducting phase transition.
Heun equation in a 5D sine-Gordon brane-world model with dilaton
International Nuclear Information System (INIS)
Cunha, M.S.; Christiansen, H.
2011-01-01
Full text: In a brane-world scenario we find the propagation modes of the gauge field in a five-dimensional space-time. We adopt warping factors of the Randall-Sundrum type which are appropriate to regularize the hierarchy problem without imposing finite compactified extra dimensions. The existence and localization of gauge particles in the ordinary four-dimensional world is studied in detail on a thick brane derived out from the equations of motion of an action with a sine-Gordon potential contribution. Maxwell zero modes together with torsion effective fields are then obtained in a gravity-dilaton background inspired in close string theories. The dilaton plays a crucial role in order that the gauge field gets localized in a conformally invariant context. Kaluza-Klein massive states are also computed and, depending on certain parameters like dilaton coupling constant and asymptotic curvature, we are able to do it fully analytically. In a general approach we find that the solutions are of the Heun type. In some specific cases we can show that the Heun general solutions can be transformed into hypergeometric functions. In others, confluent Heun solutions can be transformed into simpler functions like Mathieu functions. Exact mass spectra are found in several cases. In others, we performed numerical calculations that show a well behaved phenomenology as well. In all the cases, Kaluza-Klein modes are strongly suppressed on the brane in the effective four-dimensional theory. (author)
Higgs-dilaton cosmology: An inflation-dark-energy connection and forecasts for future galaxy surveys
Casas, Santiago; Pauly, Martin; Rubio, Javier
2018-02-01
The Higgs-dilaton model is a scale-invariant extension of the Standard Model nonminimally coupled to gravity and containing just one additional degree of freedom on top of the Standard Model particle content. This minimalistic scenario predicts a set of measurable consistency relations between the inflationary observables and the dark-energy equation-of-state parameter. We present an alternative derivation of these consistency relations that highlights the connections and differences with the α -attractor scenario. We study how far these constraints allow one to distinguish the Higgs-dilaton model from Λ CDM and w CDM cosmologies. To this end we first analyze existing data sets using a Markov chain Monte Carlo approach. Second, we perform forecasts for future galaxy surveys using a Fisher matrix approach, both for galaxy clustering and weak lensing probes. Assuming that the best fit values in the different models remain comparable to the present ones, we show that both Euclid- and SKA2-like missions will be able to discriminate a Higgs-dilaton cosmology from Λ CDM and w CDM .
Global geometry of two-dimensional charged black holes
International Nuclear Information System (INIS)
Frolov, Andrei V.; Kristjansson, Kristjan R.; Thorlacius, Larus
2006-01-01
The semiclassical geometry of charged black holes is studied in the context of a two-dimensional dilaton gravity model where effects due to pair-creation of charged particles can be included in a systematic way. The classical mass-inflation instability of the Cauchy horizon is amplified and we find that gravitational collapse of charged matter results in a spacelike singularity that precludes any extension of the spacetime geometry. At the classical level, a static solution describing an eternal black hole has timelike singularities and multiple asymptotic regions. The corresponding semiclassical solution, on the other hand, has a spacelike singularity and a Penrose diagram like that of an electrically neutral black hole. Extremal black holes are destabilized by pair-creation of charged particles. There is a maximally charged solution for a given black hole mass but the corresponding geometry is not extremal. Our numerical data exhibits critical behavior at the threshold for black hole formation
Interacting viscous ghost tachyon, K-essence and dilaton scalar field models of dark energy
International Nuclear Information System (INIS)
Karami, K; Fahimi, K
2013-01-01
We study the correspondence between the interacting viscous ghost dark energy model with the tachyon, K-essence and dilaton scalar field models in the framework of Einstein gravity. We consider a spatially non-flat FRW universe filled with interacting viscous ghost dark energy and dark matter. We reconstruct both the dynamics and potential of these scalar field models according to the evolutionary behavior of the interacting viscous ghost dark energy model, which can describe the accelerated expansion of the universe. Our numerical results show that the interaction and viscosity have opposite effects on the evolutionary properties of the ghost scalar field models. (paper)
Uniqueness theorem for static phantom wormholes in Einstein–Maxwell-dilaton theory
Directory of Open Access Journals (Sweden)
Boian Lazov
2018-03-01
Full Text Available We prove a uniqueness theorem for completely regular traversable electrically charged wormhole solutions in the Einstein–Maxwell-dilaton gravity with a phantom scalar field and a possible phantom electromagnetic field. In a certain region of the parameter space, determined by the asymptotic values of the scalar field and the lapse function, the regular wormholes are completely specified by their mass, scalar charge and electric charge. The argument is based on the positive energy theorem applied on an appropriate conformally transformed Riemannian space.
Evolution of the fine-structure constant in runaway dilaton models
Energy Technology Data Exchange (ETDEWEB)
Martins, C.J.A.P., E-mail: Carlos.Martins@astro.up.pt [Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Instituto de Astrofísica e Ciências do Espaço, CAUP, Rua das Estrelas, 4150-762 Porto (Portugal); Vielzeuf, P.E., E-mail: pvielzeuf@ifae.es [Institut de Física d' Altes Energies, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Barcelona) (Spain); Martinelli, M., E-mail: martinelli@thphys.uni-heidelberg.de [Institute for Theoretical Physics, University of Heidelberg, Philosophenweg 16, 69120, Heidelberg (Germany); Calabrese, E., E-mail: erminia.calabrese@astro.ox.ac.uk [Sub-department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom); Pandolfi, S., E-mail: stefania@dark-cosmology.dk [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark)
2015-04-09
We study the detailed evolution of the fine-structure constant α in the string-inspired runaway dilaton class of models of Damour, Piazza and Veneziano. We provide constraints on this scenario using the most recent α measurements and discuss ways to distinguish it from alternative models for varying α. For model parameters which saturate bounds from current observations, the redshift drift signal can differ considerably from that of the canonical ΛCDM paradigm at high redshifts. Measurements of this signal by the forthcoming European Extremely Large Telescope (E-ELT), together with more sensitive α measurements, will thus dramatically constrain these scenarios.
Evolution of the fine-structure constant in runaway dilaton models
International Nuclear Information System (INIS)
Martins, C.J.A.P.; Vielzeuf, P.E.; Martinelli, M.; Calabrese, E.; Pandolfi, S.
2015-01-01
We study the detailed evolution of the fine-structure constant α in the string-inspired runaway dilaton class of models of Damour, Piazza and Veneziano. We provide constraints on this scenario using the most recent α measurements and discuss ways to distinguish it from alternative models for varying α. For model parameters which saturate bounds from current observations, the redshift drift signal can differ considerably from that of the canonical ΛCDM paradigm at high redshifts. Measurements of this signal by the forthcoming European Extremely Large Telescope (E-ELT), together with more sensitive α measurements, will thus dramatically constrain these scenarios
EVH black hole solutions with higher derivative corrections
International Nuclear Information System (INIS)
Yavartanoo, Hossein
2012-01-01
We analyze the effect of higher derivative corrections to the near horizon geometry of the extremal vanishing horizon (EVH) black hole solutions in four dimensions. We restrict ourselves to a Gauss-Bonnet correction with a dilation dependent coupling in an Einstein-Maxwell-dilaton theory. This action may represent the effective action as it arises in tree level heterotic string theory compactified to four dimensions or the K3 compactification of type II string theory. We show that EVH black holes, in this theory, develop an AdS 3 throat in their near horizon geometry. (orig.)
Higher-curvature corrections to holographic entanglement with momentum dissipation
Energy Technology Data Exchange (ETDEWEB)
Tanhayi, M.R. [Islamic Azad University Central Tehran Branch (IAUCTB), Department of Physics, Faculty of Basic Science, Tehran (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), School of Physics, Tehran (Iran, Islamic Republic of); Vazirian, R. [Islamic Azad University Central Tehran Branch (IAUCTB), Department of Physics, Faculty of Basic Science, Tehran (Iran, Islamic Republic of)
2018-02-15
We study the effects of Gauss-Bonnet corrections on some nonlocal probes (entanglement entropy, n-partite information and Wilson loop) in the holographic model with momentum relaxation. Higher-curvature terms as well as scalar fields make in fact nontrivial corrections to the coefficient of the universal term in entanglement entropy. We use holographic methods to study such corrections. Moreover, holographic calculation indicates that mutual and tripartite information undergo a transition beyond which they identically change their values. We find that the behavior of the transition curves depends on the sign of the Gauss-Bonnet coupling λ. The transition for λ > 0 takes place in larger separation of subsystems than that of λ < 0. Finally, we examine the behavior of modified part of the force between external point-like objects as a function of Gauss-Bonnet coupling and its sign. (orig.)
International Nuclear Information System (INIS)
Zanzi, Andrea
2010-01-01
The chameleonic behavior of the string theory dilaton is suggested. Some of the possible consequences of the chameleonic string dilaton are analyzed in detail. In particular, (1) we suggest a new stringy solution to the cosmological constant problem and (2) we point out the nonequivalence of different conformal frames at the quantum level. In order to obtain these results, we start taking into account the (strong coupling) string loop expansion in the string frame (S-frame), therefore the so-called form factors are present in the effective action. The correct dark energy scale is recovered in the Einstein frame (E-frame) without unnatural fine-tunings and this result is robust against all quantum corrections, granted that we assume a proper structure of the S-frame form factors in the strong coupling regime. At this stage, the possibility still exists that a certain amount of fine-tuning may be required to satisfy some phenomenological constraints. Moreover in the E-frame, in our proposal, all the interactions are switched off on cosmological length scales (i.e., the theory is IR-free), while higher derivative gravitational terms might be present locally (on short distances) and it remains to be seen whether these facts clash with phenomenology. A detailed phenomenological analysis is definitely necessary to clarify these points.
Conformal internal symmetry of 2d σ-models coupled to gravity and a dilaton
International Nuclear Information System (INIS)
Julia, B.
1996-01-01
General relativity reduced to two dimensions possesses a large group of symmetries that exchange classical solutions. The associated Lie algebra is known to contain the affine Kac-Moody algebra A 1 (1) and half of a real Witt algebra. In this paper we exhibit the full symmetry under the semi-direct product of Lie(A 1 (1) ) by the Witt algebra Lie(W). Furthermore we exhibit the corresponding hidden gauge symmetries. We show that the theory can be understood in terms of an infinite dimensional potential space involving all degrees of freedom: the dilaton as well as matter and gravitation. In the dilaton sector the linear system that extends the previously known Lax pair has the form of a twisted self-duality constraint that is the analog of the self-duality constraint arising in extended supergravities in higher space-time dimensions. Our results furnish a group theoretical explanation for the simultaneous occurrence of two spectral parameters, a constant one (=y) and a variable one (=t). They hold for all 2d non-linear σ-models that are obtained by dimensional reduction of G/H models in three dimensions coupled to pure gravity. (orig./WL) (orig.)
U-duality and symplectic formulation of dilaton-axion gravity
International Nuclear Information System (INIS)
Gal'tsov, D.V.; Kechkin, O.V.
1995-07-01
We study a bosonic four-dimensional effective action corresponding to the heterotic string compactified on a 6-torus (dilaton-axion gravity with one vector field) on a curved space-time manifold possessing a time-like Killing vector field. Previously an existence of the SO(2,3) ∼ Sp(4,R) global symmetry (U-duality) as well as the symmetric space property of the corresponding σ-model have been established following Neugebauer and Kramer approach. Here we present an explicit form of the Sp(4,R) generators in terms of coset variables and construct a representation of the coset in terms of the physical target space coordinates. Complex symmetric 2 x 2 matrix Z (''matrix dilaton - axion'') is then introduced for which U-duality takes the matrix valued SL(2,R) form. In terms of this matrix the theory is further presented as a Kaehler σ-model. This leads to a more concise 2 x 2 formulation which opens new ways to construct exact classical solution. New solution (corresponding to constant ImZ) is obtained which describes the system of point massless magnetic monopoles endowed with axion charges equal to minus monopole charges. In such a system mutual magnetic repulsion is exactly balanced by axion attraction so that the resulting space-time is locally flat but possess multiple Taub-NUT singularities. (author). 35 refs
A numerical algorithm for modelling boson-fermion stars in dilatonic gravity
Boyadzhiev, T L; Todorov, M D; Yazadjiev, S S
2002-01-01
We investigate numerically the class of models of the static spherically symmetric boson-fermion stars in the scalar-tensor theory of gravity with massive dilaton field. The proper mathematical model of such stars is interpreted as a nonlinear two-parametric eigenvalue problem. The first of the parameters is the unknown internal boundary (the radius of the fermionic part of the star) R sub s , and the second one represents the frequency OMEGA of the time oscillations of the boson field. To solve this problem, the whole space [0, infinity) is splitted into two domains: internal [0, R sub s] (inside the star) and external [R sub s , infinity) (outside the star). In each domain the physical model leads to two nonlinear boundary value problems in respect to metric functions, the functions describing the fermionic and bosonic matter, and the dilaton field. These boundary value problems have different dimensions inside and outside the star, respectively. The solutions in these regions are obtained separately and ma...
Exactly solvable models of two-dimensional dilaton cosmology with quantum backreaction
International Nuclear Information System (INIS)
Zaslavskii, O B
2003-01-01
We consider a general approach to exactly solvable 2D dilaton cosmology with one-loop backreaction from conformal fields taken into account. It includes as particular cases previous models discussed in the literature. We list different types of solutions and investigate their properties for simple models, typical for string theory. We find a rather rich class of everywhere-regular solutions, which exist practically in every type of analysed solution. They exhibit different kinds of asymptotic behaviour in the past and future, including inflation, superinflation, deflation, power expansion or contraction. In particular, for some models the dS spacetime with a time-dependent dilaton field is the exact solution of the field equations. For some kinds of solution the weak-energy condition is violated independently of a specific model. We also find the solutions with a singularity which is situated in an infinite past (or future), so at any finite moment of a comoving time the universe is singularity-free. It is pointed out that for some models the spacetime may be everywhere regular even in spite of infinitely large quantum backreaction in an infinite past
Conformal internal symmetry of 2d σ-models coupled to gravity and a dilaton
International Nuclear Information System (INIS)
Julia, B.; Nicolai, H.
1996-08-01
General relativity reduced to two dimensions possesses a large group of symmetries that exchange classical solutions. The associated Lie algebra is known to contain the affine Kac-Moody algebra A 1 (1) and half of a real Witt algebra. In this paper we exhibit the full symmetry under the semi-direct product of Lie(A 1 (1) ) by the Witt algebra Lie(W). Furthermore we exhibit the corresponding hidden gauge symmetries. We show that the theory can be understood in terms of an infinite dimensional potential space involving all degrees of freedom: The dilaton as well as matter and gravitation. In the dilaton sector the linear system that extends the previously known Lax pair has the form of a twisted self-duality constraint that is the analog of the self-duality constraint arising in extended supergravities in higher spacetime dimensions. Our results furnish a group theoretical explanation for the simultaneous occurrence of two spectral parameters, a constant one (=y) and a variable one (=t). They hold for all 2d non-linear σ-models that are obtained by dimensional reduction of G/H models in three dimensions coupled to pure gravity. In that case the Lie algebra is Lie(W∝G (1) ); this symmetry acts on a set of off shell fields (in a fixed gauge) and preserves the equations of motion. (orig.)
Do stringy corrections stabilize colored black holes?
International Nuclear Information System (INIS)
Kanti, P.; Winstanley, E.
2000-01-01
We consider hairy black hole solutions of Einstein-Yang-Mills-dilaton theory, coupled to a Gauss-Bonnet curvature term, and we study their stability under small, spacetime-dependent perturbations. We demonstrate that stringy corrections do not remove the sphaleronic instabilities of colored black holes with the number of unstable modes being equal to the number of nodes of the background gauge function. In the gravitational sector and in the limit of an infinitely large horizon, colored black holes are also found to be unstable. Similar behavior is exhibited by magnetically charged black holes while the bulk of neutral black holes are proved to be stable under small, gauge-dependent perturbations. Finally, electrically charged black holes are found to be characterized only by the existence of a gravitational sector of perturbations. As in the case of neutral black holes, we demonstrate that for the bulk of electrically charged black holes no unstable modes arise in this sector. (c) 2000 The American Physical Society
Energy Technology Data Exchange (ETDEWEB)
Karami, K., E-mail: KKarami@uok.ac.i [Department of Physics, University of Kurdistan, Pasdaran St., Sanandaj (Iran, Islamic Republic of); Research Institute for Astronomy and Astrophysics of Maragha (RIAAM), Maragha (Iran, Islamic Republic of); Khaledian, M.S.; Felegary, F.; Azarmi, Z. [Department of Physics, University of Kurdistan, Pasdaran St., Sanandaj (Iran, Islamic Republic of)
2010-03-29
We study the correspondence between the tachyon, K-essence and dilaton scalar field models with the interacting new agegraphic dark energy model in the non-flat FRW universe. We reconstruct the potentials and the dynamics for these scalar field models, which describe accelerated expansion of the universe.
International Nuclear Information System (INIS)
Karami, K.; Khaledian, M.S.; Felegary, F.; Azarmi, Z.
2010-01-01
We study the correspondence between the tachyon, K-essence and dilaton scalar field models with the interacting new agegraphic dark energy model in the non-flat FRW universe. We reconstruct the potentials and the dynamics for these scalar field models, which describe accelerated expansion of the universe.
Poisson-Lie T-duality of string effective actions: A new approach to the dilaton puzzle
Czech Academy of Sciences Publication Activity Database
Jurčo, B.; Vysoký, Jan
2018-01-01
Roč. 130, August (2018), s. 1-26 ISSN 0393-0440 Institutional support: RVO:67985840 Keywords : Poisson-Lie T-duality * string effective actions * dilaton field Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 0.819, year: 2016 https://www.sciencedirect.com/science/article/pii/S0393044018301748?via%3Dihub
International Nuclear Information System (INIS)
Akarsu, Özgür; Dereli, Tekin
2013-01-01
We present cosmological solutions for (1+3+n)-dimensional steady state universe in dilaton gravity with an arbitrary dilaton coupling constant w and exponential dilaton self-interaction potentials in the string frame. We focus particularly on the class in which the 3-space expands with a time varying deceleration parameter. We discuss the number of the internal dimensions and the value of the dilaton coupling constant to determine the cases that are consistent with the observed universe and the primordial nucleosynthesis. The 3-space starts with a decelerated expansion rate and evolves into accelerated expansion phase subject to the values of w and n, but ends with a Big Rip in all cases. We discuss the cosmological evolution in further detail for the cases w = 1 and w = ½ that permit exact solutions. We also comment on how the universe would be conceived by an observer in four dimensions who is unaware of the internal dimensions and thinks that the conventional general relativity is valid at cosmological scales
Akarsu, Özgür; Dereli, Tekin
2013-02-01
We present cosmological solutions for (1+3+n)-dimensional steady state universe in dilaton gravity with an arbitrary dilaton coupling constant w and exponential dilaton self-interaction potentials in the string frame. We focus particularly on the class in which the 3-space expands with a time varying deceleration parameter. We discuss the number of the internal dimensions and the value of the dilaton coupling constant to determine the cases that are consistent with the observed universe and the primordial nucleosynthesis. The 3-space starts with a decelerated expansion rate and evolves into accelerated expansion phase subject to the values of w and n, but ends with a Big Rip in all cases. We discuss the cosmological evolution in further detail for the cases w = 1 and w = ½ that permit exact solutions. We also comment on how the universe would be conceived by an observer in four dimensions who is unaware of the internal dimensions and thinks that the conventional general relativity is valid at cosmological scales.
Poisson-Lie T-duality of string effective actions: A new approach to the dilaton puzzle
Czech Academy of Sciences Publication Activity Database
Jurčo, B.; Vysoký, Jan
2018-01-01
Roč. 130, August (2018), s. 1-26 ISSN 0393-0440 Institutional support: RVO:67985840 Keywords : Poisson-Lie T- dual ity * string effective actions * dilaton field Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 0.819, year: 2016 https://www.sciencedirect.com/science/article/pii/S0393044018301748?via%3Dihub
Fermion emission in a two-dimensional black hole space-time
International Nuclear Information System (INIS)
Wanders, G.
1994-01-01
We investigate massless fermion production by a two-dimensional dilatonic black hole. Our analysis is based on the Bogoliubov transformation relating the outgoing fermion field observed outside the black hole horizon to the incoming field present before the black hole creation. It takes full account of the fact that the transformation is neither invertible nor unitarily implementable. The particle content of the outgoing radiation is specified by means of inclusive probabilities for the detection of sets of outgoing fermions and antifermions in given states. For states localized near the horizon these probabilities characterize a thermal equilibrium state. The way the probabilities become thermal as one approaches the horizon is discussed in detail
DEFF Research Database (Denmark)
Langkjær, Michael Alexander
2012-01-01
Pop musicians performing in black stage costume take advantage of cultural traditions relating to matters black. Stylistically, black is a paradoxical color: although a symbol of melancholy, pessimism, and renunciation, black also expresses minimalist modernity and signifies exclusivity (as is hi...
Geometric description of BTZ black hole thermodynamics
International Nuclear Information System (INIS)
Quevedo, Hernando; Sanchez, Alberto
2009-01-01
We study the properties of the space of thermodynamic equilibrium states of the Banados-Teitelboim-Zanelli (BTZ) black hole in (2+1) gravity. We use the formalism of geometrothermodynamics to introduce in the space of equilibrium states a two-dimensional thermodynamic metric whose curvature is nonvanishing, indicating the presence of thermodynamic interaction, and free of singularities, indicating the absence of phase transitions. Similar results are obtained for generalizations of the BTZ black hole which include a Chern-Simons term and a dilatonic field. Small logarithmic corrections of the entropy turn out to be represented by small corrections of the thermodynamic curvature, reinforcing the idea that thermodynamic curvature is a measure of thermodynamic interaction.
Thermodynamics of intersecting black branes from interacting elementary branes
Energy Technology Data Exchange (ETDEWEB)
Morita, Takeshi [Department of Physics, Shizuoka University,836 Ohya, Suruga-ku, Shizuoka 422-8529 (Japan); Shiba, Shotaro [Maskawa Institute for Science and Culture, Kyoto Sangyo University,Kamigamo-Motoyama, Kita-ku, Kyoto 603-8555 (Japan)
2015-09-14
If an Einstein-Maxwell-Dilaton system admits the extreme brane solution in which no force works between the parallel branes, the collective motion of nearly parallel branes exhibits the thermodynamical properties which are coincident with those of the corresponding black branes at low energy regime (up to unfixed numerical factors). Hence it may provide the microscopic description of the black branes (p-soup proposal). This fact motivates us to test this proposal in the intersecting black branes which have multiple brane charges and/or momentum along the brane direction. We consider the case that the multiple branes satisfy the intersection rule and feel no force when they are static, and find the agreement to the black hole thermodynamics.
Tachyon hair on two-dimensional black holes
International Nuclear Information System (INIS)
Peet, A.; Susskind, L.; Thorlacius, L.
1993-01-01
Static black holes in two-dimensional string theory can carry tachyon hair. Configurations which are nonsingular at the event horizon have a nonvanishing asymptotic energy density. Such solutions can be smoothly extended through the event horizon and have a nonvanishing energy flux emerging from the past singularity. Dynamical processes will not change the amount of tachyon hair on a black hole. In particular, there will be no tachyon hair on a black hole formed in gravitational collapse if the initial geometry is the linear dilaton vacuum. There also exist static solutions with a finite total energy, which have singular event horizons. Simple dynamical arguments suggest that black holes formed in gravitational collapse will not have tachyon hair of this type
Dehghani, M.
2018-02-01
Making use of the suitable transformation relations, the action of three-dimensional Einstein-Maxwell-dilaton gravity theory has been obtained from that of scalar-tensor modified gravity theory coupled to the Maxwell's electrodynamics as the matter field. Two new classes of the static three-dimensional charged dilatonic black holes, as the exact solutions to the coupled scalar, electromagnetic and gravitational field equations, have been obtained in the Einstein frame. Also, it has been found that the scalar potential can be written in the form of a generalized Liouville-type potential. The conserved black hole charge and masses as well as the black entropy, temperature, and electric potential have been calculated from the geometrical and thermodynamical approaches, separately. Through comparison of the results arisen from these two alternative approaches, the validity of the thermodynamical first law has been proved for both of the new black hole solutions in the Einstein frame. Making use of the canonical ensemble method, a black hole stability or phase transition analysis has been performed. Regarding the black hole heat capacity, with the black hole charge as a constant, the points of type-1 and type-2 phase transitions have been determined. Also, the ranges of the black hole horizon radius at which the Einstein black holes are thermally stable have been obtained for both of the new black hole solutions. Then making use of the inverse transformation relations, two new classes of the string black hole solutions have been obtained from their Einstein counterpart. The thermodynamics and thermal stability of the new string black hole solutions have been investigated. It has been found that thermodynamic properties of the new charged black holes are identical in the Einstein and Jordan frames.
Bergé, Joel; Brax, Philippe; Métris, Gilles; Pernot-Borràs, Martin; Touboul, Pierre; Uzan, Jean-Philippe
2018-04-01
The existence of a light or massive scalar field with a coupling to matter weaker than gravitational strength is a possible source of violation of the weak equivalence principle. We use the first results on the Eötvös parameter by the MICROSCOPE experiment to set new constraints on such scalar fields. For a massive scalar field of mass smaller than 10-12 eV (i.e., range larger than a few 1 05 m ), we improve existing constraints by one order of magnitude to |α |baryon number and to |α |baryon and the lepton numbers. We also consider a model describing the coupling of a generic dilaton to the standard matter fields with five parameters, for a light field: We find that, for masses smaller than 10-12 eV , the constraints on the dilaton coupling parameters are improved by one order of magnitude compared to previous equivalence principle tests.
Radiative Corrections to e+e-→ Zh at Future Higgs Factory in the Minimal Dilaton Model
International Nuclear Information System (INIS)
Heng Zhao-Xia; Li Dong-Wei; Zhou Hai-Jing
2015-01-01
The minimal dilaton model (MDM) extends the Standard Model by one singlet scalar called dilaton and one top quark partner called t'. In this work we investigate the t'-induced radiative correction to the Higgs-strahlung production process e + e − → Zh at future Higgs factory. We first present the analytical calculations in detail and show how to handle the ultraviolet divergence. Then we calculate the correction numerically by considering the constraints from precision electroweak data. We find that, for sinθ L = 0.2 and m t' = 1200 GeV, the correction is 0.26% and 2.1% for √s e + e - - 240 GeV, 1 TeV respectively, and a larger value can be achieved as sin θ L increases. (physics of elementary particles and fields)
Energy Technology Data Exchange (ETDEWEB)
Vecchia, Paolo Di [The Niels Bohr Institute, University of Copenhagen,Blegdamsvej 17, DK-2100 Copenhagen Ø (Denmark); Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden); Marotta, Raffaele [Istituto Nazionale di Fisica Nucleare, Sezione di Napoli,Complesso Universitario di Monte S. Angelo ed. 6, via Cintia, 80126, Napoli (Italy); Mojaza, Matin [Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut, Am Mühlenberg 1, 14476 Potsdam (Germany)
2016-12-06
We consider the tree-level scattering amplitudes in the NS-NS (Neveu-Schwarz) massless sector of closed superstrings in the case where one external state becomes soft. We compute the amplitudes generically for any number of dimensions and any number and kind of the massless closed states through the subsubleading order in the soft expansion. We show that, when the soft state is a graviton or a dilaton, the full result can be expressed as a soft theorem factorizing the amplitude in a soft and a hard part. This behavior is similar to what has previously been observed in field theory and in the bosonic string. Differently from the bosonic string, the supersymmetric soft theorem for the graviton has no string corrections at subsubleading order. The dilaton soft theorem, on the other hand, is found to be universally free of string corrections in any string theory.
DEFF Research Database (Denmark)
di Vecchia, Paolo; Marotta, Raffaele; Mojaza, Matin
2016-01-01
We consider the tree-level scattering amplitudes in the NS-NS (Neveu-Schwarz) massless sector of closed superstrings in the case where one external state becomes soft. We compute the amplitudes generically for any number of dimensions and any number and kind of the massless closed states through...... the subsubleading order in the soft expansion. We show that, when the soft state is a graviton or a dilaton, the full result can be expressed as a soft theorem factorizing the amplitude in a soft and a hard part. This behavior is similar to what has previously been observed in field theory and in the bosonic string....... Differently from the bosonic string, the supersymmetric soft theorem for the graviton has no string corrections at subsubleading order. The dilaton soft theorem, on the other hand, is found to be universally free of string corrections in any string theory....
Energy Technology Data Exchange (ETDEWEB)
Narita, Makoto [Department of Mathematics, National Taiwan University, 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan (China)
2006-12-21
We discuss the strong cosmic censorship conjecture for cosmological spacetimes in the Einstein-Yang-Mills-dilaton system. Locally rotational symmetric Bianchi I spacetimes are considered. We show local and global existence theorems for the system. Asymptotic behaviour for the spacetimes is also investigated. The curvature invariant is blowup at the initial singularities and the spacetimes are future geodesic complete. Thus, the strong cosmic censorship conjecture for the spacetimes holds.
International Nuclear Information System (INIS)
Narita, Makoto
2006-01-01
We discuss the strong cosmic censorship conjecture for cosmological spacetimes in the Einstein-Yang-Mills-dilaton system. Locally rotational symmetric Bianchi I spacetimes are considered. We show local and global existence theorems for the system. Asymptotic behaviour for the spacetimes is also investigated. The curvature invariant is blowup at the initial singularities and the spacetimes are future geodesic complete. Thus, the strong cosmic censorship conjecture for the spacetimes holds
Non-Abelian black holes in D=5 maximal gauged supergravity
International Nuclear Information System (INIS)
Cvetic, M.; Lue, H.; Pope, C. N.
2010-01-01
We investigate static non-Abelian black hole solutions of anti-de Sitter (AdS) Einstein-Yang-Mills-dilaton gravity, which is obtained as a consistent truncation of five-dimensional maximal gauged supergravity. If the dilaton is (consistently) set to zero, the remaining equations of motion, with a spherically-symmetric ansatz, may be derived from a superpotential. The associated first-order equations admit an explicit solution supported by a non-Abelian SU(2) gauge potential, which has a logarithmically growing mass term. In an extremal limit the horizon geometry becomes AdS 2 xS 3 . If the dilaton is also excited, the equations of motion cannot easily be solved explicitly, but we obtain the asymptotic form of the more general non-Abelian black holes in this case. An alternative consistent truncation, in which the Yang-Mills fields are set to zero, also admits a description in terms of a superpotential. This allows us to construct explicit wormhole solutions (neutral spherically-symmetric domain walls). These solutions may be generalized to dimensions other than five.
Spherical and planar three-dimensional anti-de Sitter black holes
International Nuclear Information System (INIS)
Zanchin, Vilson T; Miranda, Alex S
2004-01-01
The technique of dimensional reduction was used in a recent paper (Zanchin V T, Kleber A and Lemos J P S 2002 Phys. Rev. D 66 064022) where a three-dimensional (3D) Einstein-Maxwell-dilaton theory was built from the usual four-dimensional (4D) Einstein-Maxwell-Hilbert action for general relativity. Starting from a class of 4D toroidal black holes in asymptotically anti-de Sitter (AdS) spacetimes several 3D black holes were obtained and studied in such a context. In the present work we choose a particular case of the 3D action which presents Maxwell field, dilaton field and an extra scalar field, besides gravity field and a negative cosmological constant, and obtain new 3D static black hole solutions whose horizons may have spherical or planar topology. We show that there is a 3D static spherically symmetric solution analogous to the 4D Reissner-Nordstroem-AdS black hole, and obtain other new 3D black holes with planar topology. From the static spherical solutions, new rotating 3D black holes are also obtained and analysed in some detail
International Nuclear Information System (INIS)
Cai, R.
1997-01-01
By investigating the critical behavior appearing at the extremal limit of the nondilatonic, black p-branes in (d+p) dimensions, we find that some critical exponents related to the critical point obey the scaling laws. From the scaling laws we obtain that the effective spatial dimension of the nondilatonic black holes and black strings is one, and is p for the nondilatonic black p-branes. For the dilatonic black holes and black p-branes, the effective dimension will depend on the parameters in theories. Thus, we give an interpretation why the Bekenstein-Hawking entropy may be given a simple world volume interpretation only for the nondilatonic black p-branes. copyright 1997 The American Physical Society
Deformation of extremal black holes from stringy interactions
Chen, Baoyi; Stein, Leo C.
2018-04-01
Black holes are a powerful setting for studying general relativity and theories beyond GR. However, analytical solutions for rotating black holes in beyond-GR theories are difficult to find because of the complexity of such theories. In this paper, we solve for the deformation to the near-horizon extremal Kerr metric due to two example string-inspired beyond-GR theories: Einstein-dilaton-Gauss-Bonnet and dynamical Chern-Simons theory. We accomplish this by making use of the enhanced symmetry group of NHEK and the weak-coupling limit of EdGB and dCS. We find that the EdGB metric deformation has a curvature singularity, while the dCS metric is regular. From these solutions, we compute orbital frequencies, horizon areas, and entropies. This sets the stage for analytically understanding the microscopic origin of black hole entropy in beyond-GR theories.
Black Hole Hair in Higher Dimensions
International Nuclear Information System (INIS)
Cao Chao; Chen Yixin; Li Jianlong
2010-01-01
We study the property of matter in equilibrium with a static, spherically symmetric black hole in D-dimensional spacetime. It requires that this kind of matter has an equation of state ω = p r /ρ = -n/(n + 2k), k, n epsilon N (where n > 1 corresponds to a mixture of vacuum matter and 'hair' matter), which seems to be independent of D. However, when we associate this result with specific models, we find that these hairy black holes can live only in some special dimensional spacetime: (i) D = 2 + 2k/n while the black hole is surrounded by cosmic strings, which requires D is even or D epsilon N, depending on the value of n, this is consistent with some important results in superstring theory, it might reveal the relation between cosmic string and superstring in another aspect; (ii) the black hole can be surrounded by linear dilaton field only in 4-dimensional spacetime. In both cases, D = 4 is special. We also present some examples of such hairy black holes in higher dimensions, including a toy model with negative energy density. (general)
Self-Tuning at Large (Distances): 4D Description of Runaway Dilaton Capture
Burgess, C P; Williams, M
2015-01-01
We complete here a three-part study (see also arXiv:1506.08095 and 1508.00856) of how codimension-two objects back-react gravitationally with their environment, with particular interest in situations where the transverse `bulk' is stabilized by the interplay between gravity and flux-quantization in a dilaton-Maxwell-Einstein system such as commonly appears in higher-dimensional supergravity and is used in the Supersymmetric Large Extra Dimensions (SLED) program. Such systems enjoy a classical flat direction that can be lifted by interactions with the branes, giving a mass to the would-be modulus that is smaller than the KK scale. We construct the effective low-energy 4D description appropriate below the KK scale once the transverse extra dimensions are integrated out, and show that it reproduces the predictions of the full UV theory for how the vacuum energy and modulus mass depend on the properties of the branes and stabilizing fluxes. In particular we show how this 4D theory learns the news of flux quantiza...
Perfect fluid of p-branes, 2D dilaton gravity and the big-bang
International Nuclear Information System (INIS)
Borlaf, J.
2001-01-01
This paper starts by building the energy-momentum tensor of a perfect fluid of p-branes coupled to (p+4)-dimensional general relativity. Having three homogeneous and isotropic macroscopical spatial dimensions, the system gravity/fluid can be reduced to an effective theory over the branes. For the string fluid (p=1) the effective theory is nothing but the 2D dilaton gravity where the potential for the scalar field, which is the scale factor of the macroscopical space, is fixed by the state equation and the three-dimensional geometry. This theory can be solved allowing us to compare some relevant aspects in our homogeneous and isotropic string cosmologies with those of the Robertson-Walker ones. In particular, unlike the point-particle models, the existence of an initial singularity is strongly sensitive to the state equation, and it is remarkable that this model picks out the radiation state equation as the canonical case where the big-bang is kinematically forbidden. Moreover, we cannot reduce the Robertson-Walker cosmologies to the limit when the string size approaches to zero, because the existence of an upper bound on the string size is not compatible with the big-bang. Some examples are presented
Geometric properties of static Einstein-Maxwell dilaton horizons with a Liouville potential
International Nuclear Information System (INIS)
Abdolrahimi, Shohreh; Shoom, Andrey A.
2011-01-01
We study nondegenerate and degenerate (extremal) Killing horizons of arbitrary geometry and topology within the Einstein-Maxwell-dilaton model with a Liouville potential (the EMdL model) in d-dimensional (d≥4) static space-times. Using Israel's description of a static space-time, we construct the EMdL equations and the space-time curvature invariants: the Ricci scalar, the square of the Ricci tensor, and the Kretschmann scalar. Assuming that space-time metric functions and the model fields are real analytic functions in the vicinity of a space-time horizon, we study the behavior of the space-time metric and the fields near the horizon and derive relations between the space-time curvature invariants calculated on the horizon and geometric invariants of the horizon surface. The derived relations generalize similar relations known for horizons of static four- and five-dimensional vacuum and four-dimensional electrovacuum space-times. Our analysis shows that all the extremal horizon surfaces are Einstein spaces. We present the necessary conditions for the existence of static extremal horizons within the EMdL model.
Particle creation phenomenology, Dirac sea and the induced Weyl and Einstein-dilaton gravity
Energy Technology Data Exchange (ETDEWEB)
Berezin, V.A.; Dokuchaev, V.I.; Eroshenko, Yu.N., E-mail: berezin@inr.ac.ru, E-mail: dokuchaev@inr.ac.ru, E-mail: eroshenko@inr.ac.ru [Institute for Nuclear Research, Russian Academy of Sciences, 60th October Anniversary Prospect 7a, 117312 Moscow (Russian Federation)
2017-01-01
We constructed the conformally invariant model for scalar particle creation induced by strong gravitational fields. Starting from the 'usual' hydrodynamical description of the particle motion written in the Eulerian coordinates we substituted the particle number conservation law (which enters the formalism) by 'the particle creation law', proportional to the square of the Weyl tensor (following the famous result by Ya.B. Zel'dovich and A.A. Starobinsky). Then, demanding the conformal invariance of the whole dynamical system, we have got both the (Weyl)-conformal gravity and the Einstein-Hilbert gravity action integral with dilaton field. Thus, we obtained something like the induced gravity suggested first by A.D. Sakharov. It is shown that the resulting system is self-consistent. We considered also the vacuum equations. It is shown that, beside the 'empty vacuum', there may exist the 'dynamical vacuum', which is nothing more but the Dirac sea. The latter is described by the unexpectedly elegant equation which includes both the Bach and Einstein tensors and the cosmological terms.
Perfect fluid of p-branes, 2D dilaton gravity and the big-bang
Energy Technology Data Exchange (ETDEWEB)
Borlaf, J. E-mail: jborlaf@redestb.es
2001-01-15
This paper starts by building the energy-momentum tensor of a perfect fluid of p-branes coupled to (p+4)-dimensional general relativity. Having three homogeneous and isotropic macroscopical spatial dimensions, the system gravity/fluid can be reduced to an effective theory over the branes. For the string fluid (p=1) the effective theory is nothing but the 2D dilaton gravity where the potential for the scalar field, which is the scale factor of the macroscopical space, is fixed by the state equation and the three-dimensional geometry. This theory can be solved allowing us to compare some relevant aspects in our homogeneous and isotropic string cosmologies with those of the Robertson-Walker ones. In particular, unlike the point-particle models, the existence of an initial singularity is strongly sensitive to the state equation, and it is remarkable that this model picks out the radiation state equation as the canonical case where the big-bang is kinematically forbidden. Moreover, we cannot reduce the Robertson-Walker cosmologies to the limit when the string size approaches to zero, because the existence of an upper bound on the string size is not compatible with the big-bang. Some examples are presented.
International Nuclear Information System (INIS)
Mavromatos, N.E.; Miramontes, J.L.
1988-01-01
We discuss generalised functional relations between the β-functions of bosonic σ-models propagating in graviton and dilaton backgrounds and field variations of the associated effective actions based on these backgrounds. We analyse the constraints on the possible form of the proportionality (non-degenerate) tensors, imposed by classical symmetries of the associated point-like action. As an application we derive the second order [O(α')] effective action and we find that it is consistent with a ghost free combination for both fields. Moreover we show explicitly that this action is related to the one computed within the framework of string tree-amplitudes by field redefinitions. (orig.)
Lectures on Black Hole Quantum Mechanics
Wilczek, Frank
The lectures that follow were originally given in 1992, and written up only slightly later. Since then there have been dramatic developments in the quantum theory of black holes, especially in the context of string theory. None of these are reflected here. The concept of quantum hair, which is discussed at length in the lectures, is certainly of permanent interest, and I continue to believe that in some generalized form it will prove central to the whole question of how information is stored in black holes. The discussion of scattering and emission modes from various classes of black holes could be substantially simplified using modern techniques, and from currently popular perspectives the choice of examples might look eccentric. On the other hand fashions have changed rapidly in the field, and the big questions as stated and addressed here, especially as formulated for "real" black holes (nonextremal, in four-dimensional, asymptotically flat space-time, with supersymmetry broken), remain pertinent even as the tools to address them may evolve. The four lectures I gave at the school were based on two lengthy papers that have now been published, "Black Holes as Elementary Particles," Nuclear Physics B380, 447 (1992) and "Quantum Hair on Black Holes," Nuclear Physics B378, 175 (1992). The unifying theme of this work is to help make plausible the possibility that black holes, although they are certainly unusual and extreme states of matter, may be susceptible to a description using concepts that are not fundamentally different from those we use in describing other sorts of quantum-mechanical matter. In the first two lectures I discussed dilaton black holes. The fact that apparently innocuous changes in the "matter" action can drastically change the properties of a black hole is already very significant: it indicates that the physical properties of small black holes cannot be discussed reliably in the abstract, but must be considered with due regard to the rest of
International Nuclear Information System (INIS)
Emparan, Roberto; Reall, Harvey S
2006-01-01
A black ring is a five-dimensional black hole with an event horizon of topology S 1 x S 2 . We provide an introduction to the description of black rings in general relativity and string theory. Novel aspects of the presentation include a new approach to constructing black ring coordinates and a critical review of black ring microscopics. (topical review)
Black hole production in particle collisions and higher curvature gravity
International Nuclear Information System (INIS)
Rychkov, Vyacheslav S.
2004-01-01
The problem of black hole production in trans-Planckian particle collisions is revisited, in the context of large extra dimensions scenarios of TeV-scale gravity. The validity of the standard description of this process (two colliding Aichelburg-Sexl shock waves in classical Einstein gravity) is questioned. It is observed that the classical spacetime has large curvature along the transverse collision plane, as signaled by the curvature invariant (R μνλσ ) 2 . Thus quantum gravity effects, and in particular higher curvature corrections to the Einstein gravity, cannot be ignored. To give a specific example of what may happen, the collision is reanalyzed in the Einstein-Lanczos-Lovelock gravity theory, which modifies the Einstein-Hilbert Lagrangian by adding a particular 'Gauss-Bonnet' combination of curvature squared terms. The analysis uses a series of approximations, which reduce the field equations to a tractable second order nonlinear PDE of the Monge-Ampere type. It is found that the resulting spacetime is significantly different from the pure Einstein case in the future of the transverse collision plane. These considerations cast serious doubts on the geometric cross section estimate, which is based on the classical Einstein gravity description of the black hole production process
Bergé, Joel; Brax, Philippe; Métris, Gilles; Pernot-Borràs, Martin; Touboul, Pierre; Uzan, Jean-Philippe
2018-04-06
The existence of a light or massive scalar field with a coupling to matter weaker than gravitational strength is a possible source of violation of the weak equivalence principle. We use the first results on the Eötvös parameter by the MICROSCOPE experiment to set new constraints on such scalar fields. For a massive scalar field of mass smaller than 10^{-12} eV (i.e., range larger than a few 10^{5} m), we improve existing constraints by one order of magnitude to |α|difference between the baryon and the lepton numbers. We also consider a model describing the coupling of a generic dilaton to the standard matter fields with five parameters, for a light field: We find that, for masses smaller than 10^{-12} eV, the constraints on the dilaton coupling parameters are improved by one order of magnitude compared to previous equivalence principle tests.
Fermion zero modes and the black-hole hypermultiplet with rigid supersymmetry
International Nuclear Information System (INIS)
Brooks, R.; Kallosh, R.; Ortin, T.
1995-01-01
The gravitini zero modes riding on top of the extreme Reissner-Nordstroem black-hole solution of N=2 supergravity are shown to be normalizable. The gravitini and dilatini zero modes of axion-dilaton extreme black-hole solutions of N=4 supergravity are also given and found to have finite norms. These norms are duality invariant. The finiteness and positivity of the norms in both cases are found to be correlated with the Witten-Israel-Nester construction; however, we have replaced the Witten condition by the pure-spin-3/2 constraint on the gravitini. We compare our calculation of the norms with the calculations which provide the moduli space metric for extreme black holes. The action of the N=2 hypermultiplet with an off-shell central charge describes the solitons of N=2 supergravity. This action, in the Majumdar-Papapetrou multi-black-hole background, is shown to be N=2 rigidly supersymmetric
International Nuclear Information System (INIS)
Feast, M.W.
1981-01-01
This article deals with two questions, namely whether it is possible for black holes to exist, and if the answer is yes, whether we have found any yet. In deciding whether black holes can exist or not the central role in the shaping of our universe played by the forse of gravity is discussed, and in deciding whether we are likely to find black holes in the universe the author looks at the way stars evolve, as well as white dwarfs and neutron stars. He also discusses the problem how to detect a black hole, possible black holes, a southern black hole, massive black holes, as well as why black holes are studied
Self-tuning at large (distances): 4D description of runaway dilaton capture
Energy Technology Data Exchange (ETDEWEB)
Burgess, C.P. [Physics & Astronomy, McMaster University,1280 Main St. W., Hamilton, L8S 4M1 ON (Canada); Perimeter Institute for Theoretical Physics,31 Caroline St. N., Waterloo, N2L 2Y5 ON (Canada); Division PH-TH, CERN,CH-1211, Genève 23 (Switzerland); Diener, Ross [Physics & Astronomy, McMaster University,1280 Main St. W., Hamilton, L8S 4M1 ON (Canada); Perimeter Institute for Theoretical Physics,31 Caroline St. N., Waterloo, N2L 2Y5 ON (Canada); Williams, M. [Instituut voor Theoretische Fysica, KU Leuven,Celestijnenlaan 200D, B-3001 Leuven (Belgium)
2015-10-27
We complete here a three-part study (see also http://arxiv.org/abs/1506.08095 and http://arxiv.org/abs/1508.00856) of how codimension-two objects back-react gravitationally with their environment, with particular interest in situations where the transverse ‘bulk’ is stabilized by the interplay between gravity and flux-quantization in a dilaton-Maxwell-Einstein system such as commonly appears in higher-dimensional supergravity and is used in the Supersymmetric Large Extra Dimensions (SLED) program. Such systems enjoy a classical flat direction that can be lifted by interactions with the branes, giving a mass to the would-be modulus that is smaller than the KK scale. We construct the effective low-energy 4D description appropriate below the KK scale once the transverse extra dimensions are integrated out, and show that it reproduces the predictions of the full UV theory for how the vacuum energy and modulus mass depend on the properties of the branes and stabilizing fluxes. In particular we show how this 4D theory learns the news of flux quantization through the existence of a space-filling four-form potential that descends from the higher-dimensional Maxwell field. We find a scalar potential consistent with general constraints, like the runaway dictated by Weinberg’s theorem. We show how scale-breaking brane interactions can give this potential minima for which the extra-dimensional size, ℓ, is exponentially large relative to underlying physics scales, r{sub B}, with ℓ{sup 2}=r{sub B}{sup 2}e{sup −φ} where −φ≫1 can be arranged with a small hierarchy between fundamental parameters. We identify circumstances where the potential at the minimum can (but need not) be parametrically suppressed relative to the tensions of the branes, provide a preliminary discussion of the robustness of these results to quantum corrections, and discuss the relation between what we find and earlier papers in the SLED program.
Phantom black holes and critical phenomena
Energy Technology Data Exchange (ETDEWEB)
Azreg-Aïnou, Mustapha [Engineering Faculty, Başkent University, Bağlıca Campus, Ankara (Turkey); Marques, Glauber T. [Universidade Federal Rural da Amazônia ICIBE-LASIC, Av. Presidente Tancredo Neves 2501, CEP 66077-901—Belém/PA (Brazil); Rodrigues, Manuel E., E-mail: azreg@baskent.edu.tr, E-mail: gtadaiesky@hotmail.com, E-mail: esialg@gmail.com [Faculdade de Ciências Exatas e Tecnologia, Universidade Federal do Pará, Campus Universitário de Abaetetuba, CEP 68440-000, Abaetetuba, Pará (Brazil)
2014-07-01
We consider the two classes cosh and sinh of normal and phantom black holes of Einstein-Maxwell-dilaton theory. The thermodynamics of these holes is characterized by heat capacities that may have both signs depending on the parameters of the theory. Leaving aside the normal Reissner-Nordström black hole, it is shown that only some phantom black holes of both classes exhibit critical phenomena. The two classes share a nonextremality, but special, critical point where the transition is continuous and the heat capacity, at constant charge, changes sign with an infinite discontinuity. This point yields a classification scheme for critical points. It is concluded that the two unstable and stable phases coexist on one side of the criticality state and disappear on the other side, that is, there is no configuration where only one phase exists. The sinh class has an extremality critical point where the entropy diverges. The transition from extremality to nonextremality with the charge held constant is accompanied by a loss of mass and an increase in the temperature. A special case of this transition is when the hole is isolated (microcanonical ensemble), it will evolve by emission of energy, which results in a decrease of its mass, to the final state of minimum mass and vanishing heat capacity. The Ehrenfest scheme of classification is inaccurate in this case but the generalized one due to Hilfer leads to conclude that the transition is of order less than unity. Fluctuations near criticality are also investigated.
Watts, Thomas D.; Wright, Roosevelt
1988-01-01
Examines some aspects of the problem of alcoholism among Blacks, asserting that Black alcoholism can best be considered in an ecological, environmental, sociocultural, and public health context. Notes need for further research on alcoholism among Blacks and for action to reduce the problem of Black alcoholism. (NB)
Brügmann, B.; Ghez, A. M.; Greiner, J.
2001-01-01
Recent progress in black hole research is illustrated by three examples. We discuss the observational challenges that were met to show that a supermassive black hole exists at the center of our galaxy. Stellar-size black holes have been studied in x-ray binaries and microquasars. Finally, numerical simulations have become possible for the merger of black hole binaries.
Scalar perturbations of two-dimensional Horava-Lifshitz black holes
International Nuclear Information System (INIS)
Cruz, Miguel; Gonzalez-Espinoza, Manuel; Saavedra, Joel; Vargas-Arancibia, Diego
2016-01-01
In this article, we study the stability of black hole solutions found in the context of dilatonic Horava-Lifshitz gravity in 1 + 1 dimensions by means of the quasinormal modes approach. In order to find the corresponding quasinormal modes, we consider the perturbations of massive and massless scalar fields minimally coupled to gravity. In both cases, we found that the quasinormal modes have a discrete spectrum and are completely imaginary, which leads to damping modes. For a massive scalar field and a non-vanishing cosmological constant, our results suggest unstable behavior for large values of the scalar field mass. (orig.)
International Nuclear Information System (INIS)
Marcus, N.; Oz, Y.
1993-01-01
We solve the equations of motion of the tachyon and the discrete states in the background of Witten's semiclassical black hole and in the exact two-dimensional dilaton-graviton background of Dijkgraaf et al. We find the exact solutions for weak fields, leading to conclusions in disagreement with previous studies of tachyons in the black hole. Demanding that a state in the black hole be well behaved at the horizon implies that it must tend asymptotically to a combination of a Seiberg and an anti-Seiberg c=1 state. For such a state to be well behaved asymptotically, it must satisfy the condition that neither its Seiberg nor its anti-Seiberg Liouville momentum is positive. Thus, although the free-field BRST cohomologies of the underlying SL(2, R) theory is the same as that of a c=1 theory, the black-hole spectrum is drastically truncated: There are no W ∞ states, and only tachyons with x-momenta vertical stroke p tach ≤m tach vertical stroke are allowed. In the Minkowski case only the static tachyon is allowed. The black hole is stable to the back reaction of these remaining tachyons, so they are good perturbations of the black hole, or 'hair'. However, this leaves only three tachyonic hairs in the black hole and seven in the exact solution. Such sparse hair is clearly irrelevant to the maintenance of coherence during black-hole evaporation. (orig.)
Thermodynamics of Acoustic Black Holes in Two Dimensions
Directory of Open Access Journals (Sweden)
Baocheng Zhang
2016-01-01
Full Text Available It is well-known that the thermal Hawking-like radiation can be emitted from the acoustic horizon, but the thermodynamic-like understanding for acoustic black holes was rarely made. In this paper, we will show that the kinematic connection can lead to the dynamic connection at the horizon between the fluid and gravitational models in two dimensions, which implies that there exists the thermodynamic-like description for acoustic black holes. Then, we discuss the first law of thermodynamics for the acoustic black hole via an intriguing connection between the gravitational-like dynamics of the acoustic horizon and thermodynamics. We obtain a universal form for the entropy of acoustic black holes, which has an interpretation similar to the entropic gravity. We also discuss the specific heat and find that the derivative of the velocity of background fluid can be regarded as a novel acoustic analogue of the two-dimensional dilaton potential, which interprets why the two-dimensional fluid dynamics can be connected to the gravitational dynamics but it is difficult for four-dimensional case. In particular, when a constraint is added for the fluid, the analogue of a Schwarzschild black hole can be realized.
Dirac fermions in nontrivial topology black hole backgrounds
International Nuclear Information System (INIS)
Gozdz, Marek; Nakonieczny, Lukasz; Rogatko, Marek
2010-01-01
We discuss the behavior of the Dirac fermions in a general spherically symmetric black hole background with a nontrivial topology of the event horizon. Both massive and massless cases are taken into account. We will conduct an analytical study of intermediate and late-time behavior of massive Dirac hair in the background of a black hole with a global monopole and dilaton black hole pierced by a cosmic string. In the case of a global monopole swallowed by a static black hole, the intermediate late-time behavior depends on the mass of the Dirac field, the multiple number of the wave mode, and the global monopole parameter. The late-time behavior is quite independent of these factors and has a decay rate proportional to t -5/6 . As far as the black hole pierced by a cosmic string is concerned, the intermediate late-time behavior depends only on the hair mass and the multipole number of the wave mode, while the late-time behavior dependence is the same as in the previous case. The main modification stems from the topology of the S 2 sphere pierced by a cosmic string. This factor modifies the eigenvalues of the Dirac operator acting on the transverse manifold.
... mental alertness as well as learning, memory, and information processing skills. It is also used for treating headache; ... of carbamazepine. Since black tea contains caffeine, in theory taking black tea with carbamazepine might decrease the ...
Townsend, P. K.
1997-01-01
This paper is concerned with several not-quantum aspects of black holes, with emphasis on theoretical and mathematical issues related to numerical modeling of black hole space-times. Part of the material has a review character, but some new results or proposals are also presented. We review the experimental evidence for existence of black holes. We propose a definition of black hole region for any theory governed by a symmetric hyperbolic system of equations. Our definition reproduces the usu...
Horowitz, Gary T.; Teukolsky, Saul A.
1998-01-01
Black holes are among the most intriguing objects in modern physics. Their influence ranges from powering quasars and other active galactic nuclei, to providing key insights into quantum gravity. We review the observational evidence for black holes, and briefly discuss some of their properties. We also describe some recent developments involving cosmic censorship and the statistical origin of black hole entropy.
Energy Technology Data Exchange (ETDEWEB)
Cordero, Ruben; Granados, Victor D [Departamento de Fisica, Escuela Superior de Fisica y Matematicas del IPN, Unidad Profesional Adolfo Lopez Mateos, Edificio 9, 07738 Mexico DF (Mexico); Mota, Roberto D, E-mail: cordero@esfm.ipn.mx, E-mail: granados@esfm.ipn.mx, E-mail: rmotae@ipn.mx [Departamento de ICE de la Escuela Superior de IngenierIa Mecanica y Electrica del IPN, Unidad Culhuacan. Av. Santa Ana No 1000, San Francisco Culhuacan, Coyoacan Mexico DF, CP 04430 (Mexico)
2011-09-21
We find the full symmetries of the Wheeler-DeWitt equation for the Hawking and Page wormhole model and an axion-dilaton string cosmology. We show that the Wheeler-DeWitt Hamiltonian admits a U(1, 1) hidden symmetry for the Hawking and Page model and U(2, 1) for the axion-dilaton string cosmology. If we consider the existence of matter-energy renormalization, for each of these models we find that the Wheeler-DeWitt Hamiltonian accepts an additional SL(2, R) dynamical symmetry. In this case, we show that the SL(2, R) dynamical symmetry generators transform the states from one energy Hilbert eigensubspace to another. Some new wormhole-type solutions for both models are found.
The current ability to test theories of gravity with black hole shadows
Mizuno, Yosuke; Younsi, Ziri; Fromm, Christian M.; Porth, Oliver; De Laurentis, Mariafelicia; Olivares, Hector; Falcke, Heino; Kramer, Michael; Rezzolla, Luciano
2018-04-01
Our Galactic Centre, Sagittarius A*, is believed to harbour a supermassive black hole, as suggested by observations tracking individual orbiting stars1,2. Upcoming submillimetre very-long baseline interferometry images of Sagittarius A* carried out by the Event Horizon Telescope collaboration (EHTC)3,4 are expected to provide critical evidence for the existence of this supermassive black hole5,6. We assess our present ability to use EHTC images to determine whether they correspond to a Kerr black hole as predicted by Einstein's theory of general relativity or to a black hole in alternative theories of gravity. To this end, we perform general-relativistic magnetohydrodynamical simulations and use general-relativistic radiative-transfer calculations to generate synthetic shadow images of a magnetized accretion flow onto a Kerr black hole. In addition, we perform these simulations and calculations for a dilaton black hole, which we take as a representative solution of an alternative theory of gravity. Adopting the very-long baseline interferometry configuration from the 2017 EHTC campaign, we find that it could be extremely difficult to distinguish between black holes from different theories of gravity, thus highlighting that great caution is needed when interpreting black hole images as tests of general relativity.
Magnetically-charged black branes and viscosity/entropy ratios
Energy Technology Data Exchange (ETDEWEB)
Liu, Hai-Shan [Institute for Advanced Physics & Mathematics,Zhejiang University of Technology, Hangzhou 310023 (China); George P. & Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy,Texas A& M University, College Station, TX 77843 (United States); Lü, H. [Department of Physics, Beijing Normal University,Beijing 100875 (China); Pope, C.N. [George P. & Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy,Texas A& M University, College Station, TX 77843 (United States); DAMTP, Centre for Mathematical Sciences,Cambridge University, Wilberforce Road, Cambridge CB3 OWA (United Kingdom)
2016-12-19
We consider asymptotically-AdS n-dimensional black brane solutions in a theory of gravity coupled to a set of Np-form field strengths, in which the field strengths carry magnetic charges. For appropriately chosen charges, the metrics are isotropic in the (n−2) transverse directions. However, in general the field strength configurations break the full Euclidean symmetry of the (n−2)-dimensional transverse space, and the shear viscosity tensor in the dual theory is no longer isotropic. We study the linearised equations for transverse traceless metric perturbations in these backgrounds, and by employing the Kubo formula we obtain expressions for the ratios η/S of the shear viscosity components divided by the entropy density. We find that the KSS bound on the ratios η/S is generally violated in these solutions. We also extend the discussion by including a dilatonic scalar field in the theory, leading to solutions that are asymptotically Lifshitz with hyperscaling violation.
Near horizon structure of extremal vanishing horizon black holes
Directory of Open Access Journals (Sweden)
S. Sadeghian
2015-11-01
Full Text Available We study the near horizon structure of Extremal Vanishing Horizon (EVH black holes, extremal black holes with vanishing horizon area with a vanishing one-cycle on the horizon. We construct the most general near horizon EVH and near-EVH ansatz for the metric and other fields, like dilaton and gauge fields which may be present in the theory. We prove that (1 the near horizon EVH geometry for generic gravity theory in generic dimension has a three dimensional maximally symmetric subspace; (2 if the matter fields of the theory satisfy strong energy condition either this 3d part is AdS3, or the solution is a direct product of a locally 3d flat space and a d−3 dimensional part; (3 these results extend to the near horizon geometry of near-EVH black holes, for which the AdS3 part is replaced with BTZ geometry. We present some specific near horizon EVH geometries in 3, 4 and 5 dimensions for which there is a classification. We also briefly discuss implications of these generic results for generic (gauged supergravity theories and also for the thermodynamics of near-EVH black holes and the EVH/CFT proposal.
Curing Black Hole Singularities with Local Scale Invariance
Directory of Open Access Journals (Sweden)
Predrag Dominis Prester
2016-01-01
Full Text Available We show that Weyl-invariant dilaton gravity provides a description of black holes without classical space-time singularities. Singularities appear due to the ill behaviour of gauge fixing conditions, one example being the gauge in which theory is classically equivalent to standard General Relativity. The main conclusions of our analysis are as follows: (1 singularities signal a phase transition from broken to unbroken phase of Weyl symmetry; (2 instead of a singularity, there is a “baby universe” or a white hole inside a black hole; (3 in the baby universe scenario, there is a critical mass after which reducing mass makes the black hole larger as viewed by outside observers; (4 if a black hole could be connected with white hole through the “singularity,” this would require breakdown of (classical geometric description; (5 the singularity of Schwarzschild BH solution is nongeneric and so it is dangerous to rely on it in deriving general results. Our results may have important consequences for resolving issues related to information loss puzzle. Though quantum effects are still crucial and may change the proposed classical picture, a position of building quantum theory around essentially regular classical solutions normally provides a much better starting point.
Directory of Open Access Journals (Sweden)
Angela Khristin Brown
2013-07-01
Full Text Available The migration of blacks in North America through slavery became united. The population of blacks past downs a tradition of artist through art to native born citizens. The art tradition involved telling stories to each generation in black families. The black culture elevated by tradition created hope to determine their personal freedom to escape from poverty of enslavement and to establish a way of life through tradition. A way of personal freedoms was through getting a good education that lead to a better foundation and a better way of life.
International Nuclear Information System (INIS)
Levanony, Dana; Ori, Amos
2010-01-01
We study the internal structure of a two-dimensional dilatonic evaporating black hole based on the Callan, Giddings, Harvey, and Strominger model. At the semiclassical level, a (weak) spacelike singularity was previously found to develop inside the black hole. We employ here a simplified quantum formulation of spacetime dynamics in the neighborhood of this singularity, using a minisuperspace-like approach. Quantum evolution is found to be regular and well defined at the semiclassical singularity. A well-localized initial wave packet propagating towards the singularity bounces off the latter and retains its well-localized form. Our simplified quantum treatment thus suggests that spacetime may extend semiclassically beyond the singularity, and also signifies the specific extension.
Levanony, Dana; Ori, Amos
2010-05-01
We study the internal structure of a two-dimensional dilatonic evaporating black hole based on the Callan, Giddings, Harvey, and Strominger model. At the semiclassical level, a (weak) spacelike singularity was previously found to develop inside the black hole. We employ here a simplified quantum formulation of spacetime dynamics in the neighborhood of this singularity, using a minisuperspace-like approach. Quantum evolution is found to be regular and well defined at the semiclassical singularity. A well-localized initial wave packet propagating towards the singularity bounces off the latter and retains its well-localized form. Our simplified quantum treatment thus suggests that spacetime may extend semiclassically beyond the singularity, and also signifies the specific extension.
Hawking radiation of Dirac particles from the Myers-Perry black hole
International Nuclear Information System (INIS)
Mao, Pu-Jian; Jia, Lin-Yu; Li, Ran; Ren, Ji-Rong
2011-01-01
In this paper, we apply the quantum anomaly cancelation method and the effective action approach as well as the method of Damour-Ruffini-Sannan to derive Hawking radiation of Dirac particles from the Myers-Perry black hole. Using the dimensional reduction technique, we find that the fermionic field in the background of the Myers-Perry black hole can be treated as an infinite collection of quantum fields in (1+1)-dimensional background coupled with the dilaton field and the U(1) gauge field near the horizon. Thus Hawking temperature and fluxes are found. The Hawking temperature obtained agrees with the surface gravity formula while the Hawking fluxes derived from the anomaly cancelation method and the effective action approach are in complete agreement with the ones obtained from integrating the Planck distribution. (orig.)
Eikonal instability of Gauss-Bonnet-(anti-)-de Sitter black holes
Konoplya, R. A.; Zhidenko, A.
2017-05-01
Here we have shown that asymptotically anti-de Sitter (AdS) black holes in the Einstein-Gauss-Bonnet (GB) theory are unstable under linear perturbations of space-time in some region of parameters. This (eikonal) instability develops at high multipole numbers. We found the exact parametric regions of the eikonal instability and extended this consideration to asymptotically flat and de Sitter cases. The approach to the threshold of instability is driven by purely imaginary quasinormal modes, which are similar to those found recently in Grozdanov, Kaplis, and Starinets, [J. High Energy Phys. 07 (2016) 151, 10.1007/JHEP07(2016)151] for the higher curvature corrected black hole with the planar horizon. The found instability may indicate limits of holographic applicability of the GB-AdS backgrounds. Recently, through the analysis of critical behavior in AdS space-time in the presence of the Gauss-Bonnet term, it was shown [Deppe et al, Phys. Rev. Lett. 114, 071102 (2015), 10.1103/PhysRevLett.114.071102], that, if the total energy content of the AdS space-time is small, then no black holes can be formed with mass less than some critical value. A similar mass gap was also found when considering collapse of mass shells in asymptotically flat Gauss-Bonnet theories [Frolov, Phys. Rev. Lett. 115, 051102 (2015), 10.1103/PhysRevLett.115.051102]. The found instability of all sufficiently small Einstein-Gauss-Bonnet-AdS, dS and asymptotically flat black holes may explain the existing mass gaps in their formation.
Near-horizon limit of the charged BTZ black hole and AdS2 quantum gravity
International Nuclear Information System (INIS)
Cadoni, Mariano; Setare, Mohammad R.
2008-01-01
We show that the 3D charged Banados-Teitelboim-Zanelli (BTZ) black hole solution interpolates between two different 2D AdS spacetimes: a near-extremal, near-horizon AdS 2 geometry with constant dilaton and U(1) field and an asymptotic AdS 2 geometry with a linear dilaton. Thus, the charged BTZ black hole can be considered as interpolating between the two different formulations proposed until now for AdS 2 quantum gravity. In both cases the theory is the chiral half of a 2D CFT and describes, respectively, Brown-Hennaux-like boundary deformations and near-horizon excitations. The central charge c as of the asymptotic CFT is determined by 3D Newton constant G and the AdS length l, c as = 3l/G, whereas that of the near-horizon CFT also depends on the U(1) charge Q, c nh ∝lQ/√G.
Two-dimensional quantum-corrected black hole in a finite size cavity
International Nuclear Information System (INIS)
Zaslavskii, O.B.
2004-01-01
We consider the gravitation-dilaton theory (not necessarily exactly solvable), whose potentials represent a generic linear combination of an exponential and linear functions of the dilaton. A black hole, arising in such theories, is supposed to be enclosed in a cavity, where it attains thermal equilibrium, whereas outside the cavity the field is in the Boulware state. We calculate quantum corrections to the Hawking temperature T H , with the contribution from the boundary taken into account. Vacuum polarization outside the shell tends to cool the system. We find that, for the shell to be in thermal equilibrium, it cannot be placed too close to the horizon. The quantum corrections to the mass due to vacuum polarization vanish in spite of nonzero quantum stresses. We discuss also the canonical boundary conditions and show that accounting for the finiteness of the system plays a crucial role in some theories (e.g., Callan-Giddings-Harvey-Strominger), where it enables us to define the stable canonical ensemble, whereas consideration in an infinite space would predict instability
Quantum singularities in (2+1) dimensional matter coupled black hole spacetimes
International Nuclear Information System (INIS)
Unver, O.; Gurtug, O.
2010-01-01
Quantum singularities considered in the 3D Banados-Teitelboim-Zanelli (BTZ) spacetime by Pitelli and Letelier [Phys. Rev. D 77, 124030 (2008)] is extended to charged BTZ and 3D Einstein-Maxwell-dilaton gravity spacetimes. The occurrence of naked singularities in the Einstein-Maxwell extension of the BTZ spacetime both in linear and nonlinear electrodynamics as well as in the Einstein-Maxwell-dilaton gravity spacetimes are analyzed with the quantum test fields obeying the Klein-Gordon and Dirac equations. We show that with the inclusion of the matter fields, the conical geometry near r=0 is removed and restricted classes of solutions are admitted for the Klein-Gordon and Dirac equations. Hence, the classical central singularity at r=0 turns out to be quantum mechanically singular for quantum particles obeying the Klein-Gordon equation but nonsingular for fermions obeying the Dirac equation. Explicit calculations reveal that the occurrence of the timelike naked singularities in the considered spacetimes does not violate the cosmic censorship hypothesis as far as the Dirac fields are concerned. The role of horizons that clothes the singularity in the black hole cases is replaced by repulsive potential barrier against the propagation of Dirac fields.
Curvature Correction for Microiterative Optimizations with QM/MM Electronic Embedding
Czech Academy of Sciences Publication Activity Database
Rokob, Tibor András; Rulíšek, Lubomír
2012-01-01
Roč. 33, č. 12 (2012), s. 1197-1206 ISSN 0192-8651 R&D Projects: GA AV ČR(CZ) IAA400040802 Institutional research plan: CEZ:AV0Z40550506 Keywords : potential-energy surface * quasi- newton matrices * enzymatic-reactions * transition-state search * coordinate transformation problem Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.835, year: 2012
Berookhim, Boback M; Karpman, Edward; Carrion, Rafael
2015-11-01
The surgical treatment of comorbid erectile dysfunction and Peyronie's disease has long included the implantation of an inflatable penile prosthesis as well as a number of adjuvant maneuvers to address residual curvature after prosthesis placement. To review the various surgical options for addressing curvature after prosthesis placement, with specific attention paid to an original article by Wilson et al. reporting on modeling over a penile prosthesis for the management of Peyronie's disease. A literature review was performed analyzing articles reporting the management of penile curvature in patients undergoing implantation of an inflatable penile prosthesis. Reported improvement in Peyronie's deformity as well as the complication rate associated with the various surgical techniques described. Modeling is a well-established treatment modality among patients with Peyronie's disease undergoing penile prosthesis implantation. A variety of other adjuvant maneuvers to address residual curvature when modeling alone is insufficient has been presented in the literature. Over 20 years of experience with modeling over a penile prosthesis have proven the efficacy and safety of this treatment option, providing the surgeon a simple initial step for the management of residual curvature after penile implantation which allows for the use of additional adjuvant maneuvers in those with significant deformities. © 2015 International Society for Sexual Medicine.
The Crisis in Black and Black.
Hutchinson, Earl Ofari
These essays explore why the historic conflict between blacks and whites in the United States has become a crisis that divides many African Americans. The changing racial dynamic is not marked by conflicts. between the black middle class and the poor, black men and women, the black intellectual elite and rappers, black politicians and the urban…
BOOK REVIEW: Black Holes, Cosmology and Extra Dimensions Black Holes, Cosmology and Extra Dimensions
Frolov, Valeri P.
2013-10-01
flatness of the Universe, the horizon problem and isotropy of cosmological microwave background. All this material is covered in chapter seven. Chapter eight contains brief discussion of several popular inflation models. Chapter nine is devoted to the problem of the large-scale structure formation from initial quantum vacuum fluctuation during the inflation and the spectrum of the density fluctuations. It also contains remarks on the baryonic asymmetry of the Universe, baryogenesis and primordial black holes. Part III covers the material on extra dimensions. It describes how Einstein gravity is modified in the presence of one or more additional spatial dimensions and how these extra dimensions are compactified in the Kaluza-Klein scheme. The authors also discuss how extra dimensions may affect low energy physics. They present examples of higher-dimensional generalizations of the gravity with higher-in-curvature corrections and discuss a possible mechanism of self-stabilization of an extra space. A considerable part of the chapter 10 is devoted to cosmological models with extra dimensions. In particular, the authors discuss how extra dimensions can modify 'standard' inflation models. At the end of this chapter they make several remarks on a possible relation of the value of fundamental constants in our universe with the existence of extra dimensions. Finally, in chapter 11 they demonstrate that several observable properties of the Universe are closely related with the special value of the fundamental physical constants and their fine tuning. They give interesting examples of such fine tuning and summarize many other cases. The book ends with discussion of a so-called 'cascade birth of universes in multidimensional spaces' model, proposed by one of the authors. As is evident from this brief summary of topics presented in the book, many interesting areas of modern gravity and cosmology are covered. However, since the subject is so wide, this inevitably implies that the
Vontress, Clemmont E.
1970-01-01
Blacks have developed unique environmental perceptions, values, and attitudes, making it difficult for counselors to establish and maintain positive rapport. This article examines attitudinal ingredients posited by Carl Rogers for relevance to this problem, and suggests in-service training to help counselors and other professionals relate…
R. M. Krinard
1980-01-01
Black willow and other species of Salix together comprise a majority of the stocking. Cottonwood is the chief associate, particularly in the early stages, but green ash, sycamore, pecan, persimmon, waterlocust, American elm, baldcypress, red maple, sugarberry, box-elder, and in some areas, silver maple are invaders preceding the next successional stage.
... by mouth for up to 6 weeks reduces blood sugar in people with type 2 diabetes. Cancer. Diarrhea. Irritable bowel syndrome (IBS). Other conditions. ... with the dose. Diabetes: Black psyllium can lower blood sugar levels ... with type 2 diabetes by slowing down absorption of carbohydrates. Monitor blood ...
International Nuclear Information System (INIS)
Blandford, R.D.; Thorne, K.S.
1979-01-01
Following an introductory section, the subject is discussed under the headings: on the character of research in black hole astrophysics; isolated holes produced by collapse of normal stars; black holes in binary systems; black holes in globular clusters; black holes in quasars and active galactic nuclei; primordial black holes; concluding remarks on the present state of research in black hole astrophysics. (U.K.)
BTZ black hole from Poisson–Lie T-dualizable sigma models with spectators
Directory of Open Access Journals (Sweden)
A. Eghbali
2017-09-01
Full Text Available The non-Abelian T-dualization of the BTZ black hole is discussed in detail by using the Poisson–Lie T-duality in the presence of spectators. We explicitly construct a dual pair of sigma models related by Poisson–Lie symmetry. The original model is built on a 2+1-dimensional manifold M≈O×G, where G as a two-dimensional real non-Abelian Lie group acts freely on M, while O is the orbit of G in M. The findings of our study show that the original model indeed is canonically equivalent to the SL(2,R Wess–Zumino–Witten (WZW model for a given value of the background parameters. Moreover, by a convenient coordinate transformation we show that this model describes a string propagating in a spacetime with the BTZ black hole metric in such a way that a new family of the solutions to low energy string theory with the BTZ black hole vacuum metric, constant dilaton field and a new torsion potential is found. The dual model is built on a 2+1-dimensional target manifold M˜ with two-dimensional real Abelian Lie group G˜ acting freely on it. We further show that the dual model yields a three-dimensional charged black string for which the mass M and axion charge Q per unit length are calculated. After that, the structure and asymptotic nature of the dual space–time including the horizon and singularity are determined.
Thomas, Pearl
The distinguishable black theatre in America, mirroring a distinguishable black experience, is an artistic product which demands audience involvement. Both the Afro-American oral tradition and the art of gesture are integral aspects of black theatre. In addition, the tragedy found black theatre is not tragedy in the classic sense, as blacks feel…
... medlineplus.gov/ency/article/002858.htm Black widow spider To use the sharing features on this page, please enable JavaScript. The black widow spider (Latrodectus) has a shiny black body with a ...
Directory of Open Access Journals (Sweden)
Rahim Vakili
2016-06-01
Full Text Available A 2-year-old boy was born at term of healthy, non-consanguineous Iranian parents. His mother attended in the clinic with the history of sometimes discoloration of diapers after passing urine. She noticed that first at the age of one month with intensified in recent months. His Physical examination and growth parameters were normal. His mother denied taking any medication (sorbitol, nitrofurantoin, metronidazole, methocarbamol, sena and methyldopa (5. Qualitative urine examination showed dark black discoloration. By this history, alkaptonuria was the most clinical suspicious. A 24-hour-urine sample was collected and sent for quantitative measurements. The urine sample was highly positive for homogentisic acid and negative for porphyrin metabolites.
Black and super p-branes in diverse dimensions
Duff, Michael J
1994-01-01
We present a generic Lagrangian, in arbitrary spacetime dimension $D$, describing the interaction of a dilaton, a graviton and an antisymmetric tensor of arbitrary rank $d$. For each $D$~and~$d$, we find ``solitonic'' black $\\tilde{p}$-brane solutions where $\\tilde{p} = \\tilde{d} - 1$~and~ $\\tilde d = D - d - 2$. These solutions display a spacetime singularity surrounded by an event horizon, and are characterized by a mass per unit $\\tilde p$-volume, ${\\cal M}_{\\tilde{d}}$, and topological ``magnetic'' charge $g_{\\tilde{d}}$, obeying $\\kappa {\\cal M}_{\\tilde{d}} \\geq g_{\\tilde{d}}/ \\sqrt{2}$. In the extreme limit $\\kappa {\\cal M}_{\\tilde{d}}=g_{\\tilde{d}}/ \\sqrt{2}$, the singularity and event horizon coalesce. For specific values of $D$~and~$d$, these extreme solutions also exhibit supersymmetry and may be identified with previously classified heterotic, Type IIA and Type IIB super $\\tilde p$-branes. The theory also admits elementary $p$-brane solutions with ``electric'' Noether charge $e_d$, obeying the Dira...
Charged rotating black holes in four-dimensional gauged and ungauged supergravities
International Nuclear Information System (INIS)
Chong, Z.-W.; Cvetic, M.; Lue, H.; Pope, C.N.
2005-01-01
We study four-dimensional non-extremal charged rotating black holes in ungauged and gauged supergravity. In the ungauged case, we obtain rotating black holes with four independent charges, as solutions of N=2 supergravity coupled to three Abelian vector multiplets. This is done by reducing the theory along the time direction to three dimensions, where it has an O(4,4) global symmetry. Applied to the reduction of the uncharged Kerr metric, O(1,1) 4 is a subject of O(4,4) transformations generate new solutions that correspond, after lifting back to four dimensions, to the introduction of four independent electromagnetic charges. In the case where these charges are set pairwise equal, we then generalise the four-dimensional rotating black holes to solutions of gauged N=4 supergravity, with mass, angular momentum and two independent electromagnetic charges. The dilaton and axion fields are non-constant. We also find generalisations of the gauged and ungauged solutions to include the NUT parameter, and for the ungauged solutions, the acceleration parameter too. The solutions in gauged supergravity provide new gravitational backgrounds for a further study of the AdS 4 /CFT 3 correspondence at non-zero temperature
Black Silicon Solar Cells with Black Ribbons
DEFF Research Database (Denmark)
Davidsen, Rasmus Schmidt; Tang, Peter Torben; Mizushima, Io
2016-01-01
We present the combination of mask-less reactive ion etch (RIE) texturing and blackened interconnecting ribbons as a method for obtaining all-black solar panels, while using conventional, front-contacted solar cells. Black silicon made by mask-less reactive ion etching has total, average...... in the range 15.7-16.3%. The KOH-textured reference cell had an efficiency of 17.9%. The combination of black Si and black interconnecting ribbons may result in aesthetic, all-black panels based on conventional, front-contacted silicon solar cells....... reflectance below 0.5% across a 156x156 mm2 silicon (Si) wafer. Black interconnecting ribbons were realized by oxidizing copper resulting in reflectance below 3% in the visible wavelength range. Screen-printed Si solar cells were realized on 156x156 mm2 black Si substrates with resulting efficiencies...
International Nuclear Information System (INIS)
Penrose, R.
1980-01-01
Conditions for the formation of a black hole are considered, and the properties of black holes. The possibility of Cygnus X-1 as a black hole is discussed. Einstein's theory of general relativity in relation to the formation of black holes is discussed. (U.K.)
International Nuclear Information System (INIS)
Cherepashchuk, Anatolii M
2003-01-01
Methods and results of searching for stellar mass black holes in binary systems and for supermassive black holes in galactic nuclei of different types are described. As of now (June 2002), a total of 100 black hole candidates are known. All the necessary conditions Einstein's General Relativity imposes on the observational properties of black holes are satisfied for candidate objects available, thus further assuring the existence of black holes in the Universe. Prospects for obtaining sufficient criteria for reliably distinguishing candidate black holes from real black holes are discussed. (reviews of topical problems)
Konoplya, R. A.; Stuchlík, Z.; Zhidenko, A.
2018-04-01
We determine the class of axisymmetric and asymptotically flat black-hole spacetimes for which the test Klein-Gordon and Hamilton-Jacobi equations allow for the separation of variables. The known Kerr, Kerr-Newman, Kerr-Sen and some other black-hole metrics in various theories of gravity are within the class of spacetimes described here. It is shown that although the black-hole metric in the Einstein-dilaton-Gauss-Bonnet theory does not allow for the separation of variables (at least in the considered coordinates), for a number of applications it can be effectively approximated by a metric within the above class. This gives us some hope that the class of spacetimes described here may be not only generic for the known solutions allowing for the separation of variables, but also a good approximation for a broader class of metrics, which does not admit such separation. Finally, the generic form of the axisymmetric metric is expanded in the radial direction in terms of the continued fractions and the connection with other black-hole parametrizations is discussed.
N = 8 BPS black holes preserving 1/8 supersymmetry
Bertolini, M.; Frè, P.; Trigiante, M.
1999-05-01
In the context of N = 8 supergravity we consider BPS black holes that preserve 1/8 supersymmetry. It was shown in a previous paper that, modulo U-duality transformations of E7(7), the most general solution of this type can be reduced to a black hole of the STU model. In this paper we analyse this solution in detail, considering in particular its embedding in one of the possible special Kähler manifolds compatible with the consistent truncations to N = 2 supergravity, this manifold being the moduli space of the T6/icons/Journals/Common/BbbZ" ALT="BbbZ" ALIGN="MIDDLE"/>3 orbifold, that is SU(3,3)/SU(3) × U(3). This construction requires a crucial use of the solvable Lie algebra formalism. Once the group-theoretical analysis is done, starting from a static, spherically symmetric ansatz, we find an exact solution for all the scalars (both dilaton- and axion-like) and for gauge fields, together with their already known charge-dependent fixed values, which yield a U-duality-invariant entropy. We also give a complete translation dictionary between the solvable Lie algebra and the special Kähler formalisms in order to allow a more immediate comparison with other papers on similar issues. Although the explicit solution is given in a simplified case where the equations turn out to be more manageable, it encodes all the features of the more general one, namely it has non-vanishing entropy and the scalar fields have a non-trivial radial dependence.
Shoemaker, Deirdre; Smith, Kenneth; Schnetter, Erik; Fiske, David; Laguna, Pablo; Pullin, Jorge
2002-04-01
Recently, stationary black holes have been successfully simulated for up to times of approximately 600-1000M, where M is the mass of the black hole. Considering that the expected burst of gravitational radiation from a binary black hole merger would last approximately 200-500M, black hole codes are approaching the point where simulations of mergers may be feasible. We will present two types of simulations of single black holes obtained with a code based on the Baumgarte-Shapiro-Shibata-Nakamura formulation of the Einstein evolution equations. One type of simulations addresses the stability properties of stationary black hole evolutions. The second type of simulations demonstrates the ability of our code to move a black hole through the computational domain. This is accomplished by shifting the stationary black hole solution to a coordinate system in which the location of the black hole is time dependent.
Black hole critical phenomena without black holes
Indian Academy of Sciences (India)
large values of Ф, black holes do form and for small values the scalar field ... on the near side of the ridge ultimately evolve to form black holes while those configu- ... The inset shows a bird's eye view looking down on the saddle point.
Long, Richard A.
1970-01-01
Indicates tendencies dangerous to the basic purpose of Black Studies, and identifies four external challeges--imperialism, paternalism, nihilism, and materialism. An internal challenge is considered to be the use of European and Establishment constructs to analyze black reality. (DM)
International Nuclear Information System (INIS)
Banerjee, Nabamita; Mandal, Ipsita; Sen, Ashoke
2009-01-01
Macroscopic entropy of an extremal black hole is expected to be determined completely by its near horizon geometry. Thus two black holes with identical near horizon geometries should have identical macroscopic entropy, and the expected equality between macroscopic and microscopic entropies will then imply that they have identical degeneracies of microstates. An apparent counterexample is provided by the 4D-5D lift relating BMPV black hole to a four dimensional black hole. The two black holes have identical near horizon geometries but different microscopic spectrum. We suggest that this discrepancy can be accounted for by black hole hair - degrees of freedom living outside the horizon and contributing to the degeneracies. We identify these degrees of freedom for both the four and the five dimensional black holes and show that after their contributions are removed from the microscopic degeneracies of the respective systems, the result for the four and five dimensional black holes match exactly.
Energy Technology Data Exchange (ETDEWEB)
Lopez-DomInguez, J C [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); Obregon, O [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico); RamIrez, C [Facultad de Ciencias FIsico Matematicas, Universidad Autonoma de Puebla, PO Box 1364, 72000 Puebla (Mexico); Sabido, M [Instituto de Fisica de la Universidad de Guanajuato PO Box E-143, 37150 Leoen Gto. (Mexico)
2007-11-15
We study noncommutative black holes, by using a diffeomorphism between the Schwarzschild black hole and the Kantowski-Sachs cosmological model, which is generalized to noncommutative minisuperspace. Through the use of the Feynman-Hibbs procedure we are able to study the thermodynamics of the black hole, in particular, we calculate Hawking's temperature and entropy for the 'noncommutative' Schwarzschild black hole.
Larjo, Klaus; Lowe, David A.; Thorlacius, Larus
2013-05-01
The postulates of black hole complementarity do not imply a firewall for infalling observers at a black hole horizon. The dynamics of the stretched horizon, that scrambles and reemits information, determines whether infalling observers experience anything out of the ordinary when entering a large black hole. In particular, there is no firewall if the stretched horizon degrees of freedom retain information for a time of the order of the black hole scrambling time.
International Nuclear Information System (INIS)
Gibbons, G.
1976-01-01
Recent work, which has been investigating the use of the concept of entropy with respect to gravitating systems, black holes and the universe as a whole, is discussed. The resulting theory of black holes assigns a finite temperature to them -about 10 -7 K for ordinary black holes of stellar mass -which is in complete agreement with thermodynamical concepts. It is also shown that black holes must continuously emit particles just like ordinary bodies which have a certain temperature. (U.K.)
Moss, Ian G; Shiiki, N; Winstanley, E
2000-01-01
Charged black hole solutions with pion hair are discussed. These can be\\ud used to study monopole black hole catalysis of proton decay.\\ud There also exist\\ud multi-black hole skyrmion solutions with BPS monopole behaviour.
Indian Academy of Sciences (India)
First page Back Continue Last page Overview Graphics. What is black hole? Possible end phase of a star: A star is a massive, luminous ball of plasma having continuous nuclear burning. Star exhausts nuclear fuel →. White Dwarf, Neutron Star, Black Hole. Black hole's gravitational field is so powerful that even ...
Sinnette, Calvin H.
1972-01-01
Contends that the survival of black people is in serious jeopardy as is evidenced in contemporary discussions on the worldwide plight of black people, and that an exhaustive study of the problem in its many dimensions is seriously lacking; the moral and ethical issues of genocide require examination from a black perspective. (JW)
Quantum Mechanics and Black Holes in Four-Dimensional String Theory
Ellis, Jonathan Richard; Nanopoulos, Dimitri V
1992-01-01
In previous papers we have shown how strings in a two-dimensional target space reconcile quantum mechanics with general relativity, thanks to an infinite set of conserved quantum numbers, ``W-hair'', associated with topological soliton-like states. In this paper we extend these arguments to four dimensions, by considering explicitly the case of string black holes with radial symmetry. The key infinite-dimensional W-symmetry is associated with the $\\frac{SU(1,1)}{U(1)}$ coset structure of the dilaton-graviton sector that is a model-independent feature of spherically symmetric four-dimensional strings. Arguments are also given that the enormous number of string {\\it discrete (topological)} states account for the maintenance of quantum coherence during the (non-thermal) stringy evaporation process, as well as quenching the large Hawking-Bekenstein entropy associated with the black hole. Defining the latter as the measure of the loss of information for an observer at infinity, who - ignoring the higher string qua...
Energy Technology Data Exchange (ETDEWEB)
Zangeneh, M. Kord; Dehyadegari, A. [Physics Department and Biruni Observatory, College of Sciences, Shiraz University,Eram Square, Shiraz, P.O. Box 71454 (Iran, Islamic Republic of); Sheykhi, A.; Dehghani, M.H. [Physics Department and Biruni Observatory, College of Sciences, Shiraz University,Eram Square, Shiraz, P.O. Box 71454 (Iran, Islamic Republic of); Research Institute for Astrophysics and Astronomy of Maragha (RIAAM),P.O. Box 55134-441, Maragha (Iran, Islamic Republic of)
2016-03-07
In this paper, we construct a new class of topological black hole Lifshitz solutions in the presence of nonlinear exponential electrodynamics for Einstein-dilaton gravity. We show that the reality of Lifshitz supporting Maxwell matter fields exclude the negative horizon curvature solutions except for the asymptotic AdS case. Calculating the conserved and thermodynamical quantities, we obtain a Smarr type formula for the mass and confirm that thermodynamics first law is satisfied on the black hole horizon. Afterward, we study the thermal stability of our solutions and figure out the effects of different parameters on the stability of solutions under thermal perturbations. Next, we apply the gauge/gravity duality in order to calculate the ratio of shear viscosity to entropy for a three-dimensional hydrodynamic system by using the pole method. Furthermore, we study the behavior of holographic conductivity for two-dimensional systems such as graphene. We consider linear Maxwell and nonlinear exponential electrodynamics separately and disclose the effect of nonlinearity on holographic conductivity. We indicate that holographic conductivity vanishes for z>3 in the case of nonlinear electrodynamics while it does not in the linear Maxwell case. Finally, we solve perturbative additional field equations numerically and plot the behaviors of real and imaginary parts of conductivity for asymptotic AdS and Lifshitz cases. We present experimental results match with our numerical ones.
Wijers, R.A.M.J.
1996-01-01
Introduction Distinguishing neutron stars and black holes Optical companions and dynamical masses X-ray signatures of the nature of a compact object Structure and evolution of black-hole binaries High-mass black-hole binaries Low-mass black-hole binaries Low-mass black holes Formation of black holes
International Nuclear Information System (INIS)
Arsiwalla, Xerxes D.; Verlinde, Erik P.
2010-01-01
We study the problem of spatially stabilizing four dimensional extremal black holes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing black holes placed in external fields we find that taking a continuum limit of Denef et al.'s multicenter supersymmetric black hole solutions provides a supergravity description of such backgrounds within which a black hole can be trapped within a confined volume. This construction is realized by solving for a levitating black hole over a magnetic dipole base. We comment on how such a construction is akin to a mechanical levitron.
On conserved charges and thermodynamics of the AdS{sub 4} dyonic black hole
Energy Technology Data Exchange (ETDEWEB)
Cárdenas, Marcela [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile); Departamento de Física, Universidad de Concepción,Casilla 160-C, Concepción (Chile); Fuentealba, Oscar; Matulich, Javier [Centro de Estudios Científicos (CECs),Av. Arturo Prat 514, Valdivia (Chile)
2016-05-02
We consider four-dimensional gravity in the presence of a dilatonic scalar field and an Abelian gauge field. This theory corresponds to the bosonic sector of a Kaluza-Klein reduction of eleven-dimensional supergravity which induces a specific self-interacting potential for the scalar field. We compute the conserved charges and carry out the thermodynamics of an anti-de Sitter (AdS) dyonic black hole solution that was proposed recently. The charges coming from symmetries of the action are computed using the Regge-Teitelboim Hamiltonian approach. They correspond to the mass, which acquires contributions from the scalar field, and the electric charge. We introduce integrability conditions because the scalar field leads to non-integrable terms in the variation of the mass. These conditions are generically solved by introducing boundary conditions that relate the leading and subleading terms of the scalar field fall-off. The Hamiltonian Euclidean action, computed in the grand canonical ensemble, is obtained by demanding the action to have an extremum. Its value is given by a radial boundary term plus an additional polar angle boundary term due to the presence of a magnetic monopole. Remarkably, the magnetic charge can be identified from the variation of the additional polar angle boundary term, confirming that the first law of black hole thermodynamics is a consequence of having a well-defined and finite Hamiltonian action principle, even if the charge does not come from a symmetry of the action. The temperature and electrostatic potential are determined by demanding regularity of the black hole solution, whereas the value of the magnetic potential is determined by the variation of the additional polar angle boundary term. Consequently, the first law of black hole thermodynamics is identically satisfied by construction.
International Nuclear Information System (INIS)
Novikov, I.; Polnarev, A.
1981-01-01
Proves are searched for of the formation of the so-called primary black holes at the very origin of the universe. The black holes would weigh less than 10 13 kg. The formation of a primary black hole is conditional on strong fluctuations of the gravitational field corresponding roughly to a half of the fluctuation maximally permissible by the general relativity theory. Only big fluctuations of the gravitational field can overcome the forces of the hot gas pressure and compress the originally expanding matter into a black hole. Low-mass black holes have a temperature exceeding that of the black holes formed from stars. A quantum process of particle formation, the so-called evaporation takes place in the strong gravitational field of a black hole. The lower the mass of the black hole, the shorter the evaporation time. The analyses of processes taking place during the evaporation of low-mass primary black holes show that only a very small proportion of the total mass of the matter in the universe could turn into primary black holes. (M.D.)
Energy Technology Data Exchange (ETDEWEB)
DOREN,NEALL E.
1999-10-01
Wavefront curvature defocus effects occur in spotlight-mode SAR imagery when reconstructed via the well-known polar-formatting algorithm (PFA) under certain imaging scenarios. These include imaging at close range, using a very low radar center frequency, utilizing high resolution, and/or imaging very large scenes. Wavefront curvature effects arise from the unrealistic assumption of strictly planar wavefronts illuminating the imaged scene. This dissertation presents a method for the correction of wavefront curvature defocus effects under these scenarios, concentrating on the generalized: squint-mode imaging scenario and its computational aspects. This correction is accomplished through an efficient one-dimensional, image domain filter applied as a post-processing step to PF.4. This post-filter, referred to as SVPF, is precalculated from a theoretical derivation of the wavefront curvature effect and varies as a function of scene location. Prior to SVPF, severe restrictions were placed on the imaged scene size in order to avoid defocus effects under these scenarios when using PFA. The SVPF algorithm eliminates the need for scene size restrictions when wavefront curvature effects are present, correcting for wavefront curvature in broadside as well as squinted collection modes while imposing little additional computational penalty for squinted images. This dissertation covers the theoretical development, implementation and analysis of the generalized, squint-mode SVPF algorithm (of which broadside-mode is a special case) and provides examples of its capabilities and limitations as well as offering guidelines for maximizing its computational efficiency. Tradeoffs between the PFA/SVPF combination and other spotlight-mode SAR image formation techniques are discussed with regard to computational burden, image quality, and imaging geometry constraints. It is demonstrated that other methods fail to exhibit a clear computational advantage over polar-formatting in conjunction with SVPF. This research concludes that PFA in conjunction with SVPF provides a computationally efficient spotlight-mode image formation solution that solves the wavefront curvature problem for most standoff distances and patch sizes, regardless of squint, resolution or radar center frequency. Additional advantages are that SVPF is not iterative and has no dependence on the visual contents of the scene: resulting in a deterministic computational complexity which typically adds only thirty percent to the overall image formation time.
International Nuclear Information System (INIS)
Winter, J.
1985-01-01
A covariant generalization of the Wigner transformation of quantum equations is proposed for gravitating many-particle systems, which modifies the Einstein-Liouville equations for the coupled gravity-matter problem by inclusion of quantum effects of the matter moving in its self-consistent classical gravitational field, in order to extend their realm of validity to higher particle densities. The corrections of the Vlasov equation (Liouville equation in one-particle phase space) are exhibited as combined effects of quantum mechanics and the curvature of space-time arranged in a semiclassical expansion in powers of h 2 , the first-order term of which is explicitly calculated. It is linear in the Riemann tensor and in its gradient; the Riemann tensor occurs in a similar position as the tensor of the Yang-Mills field strength in a corresponding Vlasov equation for systems with local gauge invariance in the purely classical limit. The performance of the Wigner transformation is based on expressing the equation of motion for the two-point function of the Klein-Gordon field, in particular the Beltrami operator, in terms of a midpoint and a distance vector covariantly defined for the two points. This implies the calculation of deviations of the geodesic between these points, the standard concept of which has to be refined to include infinitesimal variations of the second order. A differential equation for the second-order deviation is established
Ozkuvanci, Ünsal; Ziylan, Orhan; Dönmez, M Irfan; Yucel, Omer Baris; Oktar, Tayfun; Ander, Haluk; Nane, Ismet
2017-01-01
The aim of this study is to analyze post pubertal results of pre pubertal tunica albuginea plication with non-absorbable sutures in the correction of CPC. The files of patients who underwent tunica albuginea plication without incision (dorsal/lateral) were retrospectively reviewed. Patients younger than 13 years of age at the time of operation and older than 14 years of age in November 2015 were included. Patients with a penile curvature of less than 30 degrees & more than 45 degrees and penile/urethral anomalies were excluded. All of the patients underwent surgery followed by circumcision. The mean age of patients at the time of the operation was 9.7 years (range, 6-13 years). The mean degree of ventral penile curvature measured during the operation was 39 degrees while it was 41 degrees in the lateral curvatures. All of the patients were curvature-free at the end of the operation. At the time of the follow-up examination, the mean age was 16.7 years (range, 14-25 years). Six patients had a straight (0-10 degrees) penis during erection and seven patients had recurrent penile curvatures ranging from 30 to 50 degrees. Pre pubertal tunica albuginea plication of congenital penile curvature (30-45 degrees) with non-absorbable sutures performed without incision is a minimal invasive method especially when performed during circumcision. However, recurrence might be observed in half of the patients after puberty. Copyright® by the International Brazilian Journal of Urology.
Directory of Open Access Journals (Sweden)
Ünsal Ozkuvanci
Full Text Available ABSTRACT Objective: The aim of this study is to analyze post pubertal results of pre pubertal tunica albuginea plication with non-absorbable sutures in the correction of CPC. Materials and Methods: The files of patients who underwent tunica albuginea plication without incision (dorsal/lateral were retrospectively reviewed. Patients younger than 13 years of age at the time of operation and older than 14 years of age in November 2015 were included. Patients with a penile curvature of less than 30 degrees & more than 45 degrees and penile/urethral anomalies were excluded. All of the patients underwent surgery followed by circumcision. Results: The mean age of patients at the time of the operation was 9.7 years (range, 6-13 years. The mean degree of ventral penile curvature measured during the operation was 39 degrees while it was 41 degrees in the lateral curvatures. All of the patients were curvature-free at the end of the operation. At the time of the follow-up examination, the mean age was 16.7 years (range, 14-25 years. Six patients had a straight (0-10 degrees penis during erection and seven patients had recurrent penile curvatures ranging from 30 to 50 degrees. Conclusion: Pre pubertal tunica albuginea plication of congenital penile curvature (30-45 degrees with non-absorbable sutures performed without incision is a minimal invasive method especially when performed during circumcision. However, recurrence might be observed in half of the patients after puberty.
Gorini, Vittorio; Moschella, Ugo; Treves, Aldo; Colpi, Monica
2016-01-01
Based on graduate school lectures in contemporary relativity and gravitational physics, this book gives a complete and unified picture of the present status of theoretical and observational properties of astrophysical black holes. The chapters are written by internationally recognized specialists. They cover general theoretical aspects of black hole astrophysics, the theory of accretion and ejection of gas and jets, stellar-sized black holes observed in the Milky Way, the formation and evolution of supermassive black holes in galactic centers and quasars as well as their influence on the dynamics in galactic nuclei. The final chapter addresses analytical relativity of black holes supporting theoretical understanding of the coalescence of black holes as well as being of great relevance in identifying gravitational wave signals. With its introductory chapters the book is aimed at advanced graduate and post-graduate students, but it will also be useful for specialists.
Begelman, Mitchell C.
2014-01-01
I outline the theory of accretion onto black holes, and its application to observed phenomena such as X-ray binaries, active galactic nuclei, tidal disruption events, and gamma-ray bursts. The dynamics as well as radiative signatures of black hole accretion depend on interactions between the relatively simple black-hole spacetime and complex radiation, plasma and magnetohydrodynamical processes in the surrounding gas. I will show how transient accretion processes could provide clues to these ...
Nonextremal stringy black hole
International Nuclear Information System (INIS)
Suzuki, K.
1997-01-01
We construct a four-dimensional BPS saturated heterotic string solution from the Taub-NUT solution. It is a nonextremal black hole solution since its Euler number is nonzero. We evaluate its black hole entropy semiclassically. We discuss the relation between the black hole entropy and the degeneracy of string states. The entropy of our string solution can be understood as the microscopic entropy which counts the elementary string states without any complications. copyright 1997 The American Physical Society
International Nuclear Information System (INIS)
Horowitz, G.T.; Ross, S.F.
1997-01-01
It is shown that there are large static black holes for which all curvature invariants are small near the event horizon, yet any object which falls in experiences enormous tidal forces outside the horizon. These black holes are charged and near extremality, and exist in a wide class of theories including string theory. The implications for cosmic censorship and the black hole information puzzle are discussed. copyright 1997 The American Physical Society
Wallace, Joan
The black family is the primary socializing agent of the black child and, thus, the primary educator. The culture of blacks in America, in which the child is steeped, is unique, complex and rich-the result of a convergence and fusion of African, American, and European influences. In its education of the black child, the black family must deal,…
de Boer, J.; Papadodimas, K.; Verlinde, E.
2009-01-01
Supersymmetric black holes are characterized by a large number of degenerate ground states. We argue that these black holes, like other quantum mechanical systems with such a degeneracy, are subject to a phenomenon which is called the geometric or Berry’s phase: under adiabatic variations of the
International Nuclear Information System (INIS)
Ravndal, F.
1978-01-01
Applying Einstein's theory of gravitation to black holes and their interactions with their surroundings leads to the conclusion that the sum of the surface areas of several black holes can never become less. This is shown to be analogous to entropy in thermodynamics, and the term entropy is also thus applied to black holes. Continuing, expressions are found for the temperature of a black hole and its luminosity. Thermal radiation is shown to lead to explosion of the black hole. Numerical examples are discussed involving the temperature, the mass, the luminosity and the lifetime of black mini-holes. It is pointed out that no explosions corresponding to the prediction have been observed. It is also shown that the principle of conservation of leptons and baryons is broken by hot black holes, but that this need not be a problem. The related concept of instantons is cited. It is thought that understanding of thermal radiation from black holes may be important for the development of a quantified gravitation theory. (JIW)
African Journals Online (AJOL)
(Apis meOifera) on black ironbark. (Eucalyptus sideroxylon). B. Buys. Plant Protection Research Institute, Private Bag X5017,. Stellenbosch, 7600 Republic of South Africa. Received May /984; accepted 28 November /986. Black ironbark trees secrete nectar during the night. Argentine ants collected 42% of the nectar before ...
DEFF Research Database (Denmark)
Kragh, Helge Stjernholm
2016-01-01
Review essay, Marcia Bartusiak, Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved (New Haven: Yale University Press, 2015).......Review essay, Marcia Bartusiak, Black Hole: How an Idea Abandoned by Newtonians, Hated by Einstein, and Gambled On by Hawking Became Loved (New Haven: Yale University Press, 2015)....
Hooft, G. 't
1987-01-01
This article is divided into three parts. First, a systematic derivation of the Hawking radiation is given in three different ways. The information loss problem is then discussed in great detail. The last part contains a concise discussion of black hole thermodynamics. This article was published as chapter $6$ of the IOP book "Lectures on General Relativity, Cosmology and Quantum Black Holes" (July $2017$).
Morris, Monique W.
2016-01-01
Statistics show that black girls in U.S. K-12 public schools are overrepresented among students who face disciplinary approaches (such as suspensions) that exclude or even criminalize them. Morris explains how black girls face conditions that make them vulnerable to a phenomenon she calls "school to confinement pathways"--conditions like…
Arsiwalla, X.D.; Verlinde, E.P.
2010-01-01
We study the problem of spatially stabilizing four dimensional extremal black holes in background electric/magnetic fields. Whilst looking for stationary stable solutions describing black holes placed in external fields we find that taking a continuum limit of Denef et al.’s multicenter
Hayes, Dianne
2012-01-01
Not even the first lady of the most powerful nation in the world is immune to stereotypes that have plagued Black women since first setting foot on American soil. Stereotypes of being the "angry Black woman" and curiosity about differences in appearance still persist from the academy to 1600 Pennsylvania Ave. As African-American women rise in…
Black Boycott: Gainsville, Florida
White, Arthur O.
1975-01-01
A case study of the events precipitating a black student boycott in 1969 in Gainesville, Flordia, when school board manuevering to avoid school integration led to the threatened closing of Lincoln High School, a reputable black community school. Also described are the subsequent transformations of Lincoln into a vocational-technical school and…
Lifshitz topological black holes
International Nuclear Information System (INIS)
Mann, R.B.
2009-01-01
I find a class of black hole solutions to a (3+1) dimensional theory gravity coupled to abelian gauge fields with negative cosmological constant that has been proposed as the dual theory to a Lifshitz theory describing critical phenomena in (2+1) dimensions. These black holes are all asymptotic to a Lifshitz fixed point geometry and depend on a single parameter that determines both their area (or size) and their charge. Most of the solutions are obtained numerically, but an exact solution is also obtained for a particular value of this parameter. The thermodynamic behaviour of large black holes is almost the same regardless of genus, but differs considerably for small black holes. Screening behaviour is exhibited in the dual theory for any genus, but the critical length at which it sets in is genus-dependent for small black holes.
Legitimizing Blacks in Philosophy
Directory of Open Access Journals (Sweden)
Jameliah Shorter-Bourhanou
2017-12-01
Full Text Available In its efforts toward improving diversity, the discipline of philosophy has tended to focus on increasing the number of black philosophers. One crucial issue that has received less attention is the extent to which black philosophers are delegitimized in the discipline because their philosophical contributions challenge the status quo. A systematic problem that bars black philosophers from equal and full participation, this delegitimization precludes the emergence of genuine diversity and reveals the importance of interrogating broader attitudes toward black philosophical contributions. In this essay, I argue for radical systematic changes to disciplinary hallmarks of professionalization such as pedagogy, mentoring, publishing, and hiring practices with the aim of legitimizing black philosophers and their contributions.
ULTRAMASSIVE BLACK HOLE COALESCENCE
International Nuclear Information System (INIS)
Khan, Fazeel Mahmood; Holley-Bockelmann, Kelly; Berczik, Peter
2015-01-01
Although supermassive black holes (SMBHs) correlate well with their host galaxies, there is an emerging view that outliers exist. Henize 2-10, NGC 4889, and NGC 1277 are examples of SMBHs at least an order of magnitude more massive than their host galaxy suggests. The dynamical effects of such ultramassive central black holes is unclear. Here, we perform direct N-body simulations of mergers of galactic nuclei where one black hole is ultramassive to study the evolution of the remnant and the black hole dynamics in this extreme regime. We find that the merger remnant is axisymmetric near the center, while near the large SMBH influence radius, the galaxy is triaxial. The SMBH separation shrinks rapidly due to dynamical friction, and quickly forms a binary black hole; if we scale our model to the most massive estimate for the NGC 1277 black hole, for example, the timescale for the SMBH separation to shrink from nearly a kiloparsec to less than a parsec is roughly 10 Myr. By the time the SMBHs form a hard binary, gravitational wave emission dominates, and the black holes coalesce in a mere few Myr. Curiously, these extremely massive binaries appear to nearly bypass the three-body scattering evolutionary phase. Our study suggests that in this extreme case, SMBH coalescence is governed by dynamical friction followed nearly directly by gravitational wave emission, resulting in a rapid and efficient SMBH coalescence timescale. We discuss the implications for gravitational wave event rates and hypervelocity star production
On the Charter Question: Black Marxism and Black Nationalism
Stern, Mark; Hussain, Khuram
2015-01-01
This article brings two black intellectual traditions to bear on the question of charter schools: black Marxism and black nationalism. The authors examine the theoretical and rhetorical devices used to talk about charters schools by focusing on how notions of "black liberation" are deployed by the charter movement, and to what end. The…
"Black Like Me": Reframing Blackness for Decolonial Politics
Dei, George J. Sefa
2018-01-01
From a particular vantage point, as an African-born scholar with a politics to affirm my Black subjectivity and Indigeneity in a diasporic context, my article engages a (re)theorization of Blackness for decolonial politics. Building on existing works of how Black scholars, themselves, have theorized Blackness, and recognizing the fluid,…
Hayward, Sean Alan
2013-01-01
Black holes, once just fascinating theoretical predictions of how gravity warps space-time according to Einstein's theory, are now generally accepted as astrophysical realities, formed by post-supernova collapse, or as supermassive black holes mysteriously found at the cores of most galaxies, powering active galactic nuclei, the most powerful objects in the universe. Theoretical understanding has progressed in recent decades with a wider realization that local concepts should characterize black holes, rather than the global concepts found in textbooks. In particular, notions such as trapping h
Understanding the Black Aesthetic Experience.
Curtis, Marvin V.
1988-01-01
Discussing the importance of the Black aesthetic experience, Curtis examines Black cultural heritage and participatory style, the spiritual, and the creation and recreation of Black music. Advocating multicultural music education in teacher training, he suggests that Black music be studied for its value and contribution to society. Lists five ways…
New Directions for Black Women?
McGuigan, Dorothy, Ed.
1978-01-01
This collection of papers deals with various aspects of the black female experience in America. "The Black Woman in Transition" discusses the effects of sexism and racism on black women with particular reference to employment and education; it is noted that black women, in comparison with other groups in society, suffer a proportionately higher…
Black Writers' Views of America.
Hairston, Loyle
1979-01-01
This article argues that the stagnation, pessimism, and self-pity evident in recent Black writing results in part from the alienation of Black writers from the mainstream of Black life, and in part from the illusions that they share with other Blacks who have embraced the American value system. (Author/EB)
Monten, Ruben; Toldo, Chiara
2018-02-01
We present new AdS4 black hole solutions in N =2 gauged supergravity coupled to vector and hypermultiplets. We focus on a particular consistent truncation of M-theory on the homogeneous Sasaki–Einstein seven-manifold M 111, characterized by the presence of one Betti vector multiplet. We numerically construct static and spherically symmetric black holes with electric and magnetic charges, corresponding to M2 and M5 branes wrapping non-contractible cycles of the internal manifold. The novel feature characterizing these nonzero temperature configurations is the presence of a massive vector field halo. Moreover, we verify the first law of black hole mechanics and we study the thermodynamics in the canonical ensemble. We analyze the behavior of the massive vector field condensate across the small-large black hole phase transition and we interpret the process in the dual field theory.
... are reported in blacks received training to enhance skills for engaging communities, develop strategies, and sustain partnerships for reducing TB rates. Other CDC activities include a study to identify the socio-cultural, racial, and health ...
Ruffini, Remo; Wheeler, John A.
1971-01-01
discusses the cosmology theory of a black hole, a region where an object loses its identity, but mass, charge, and momentum are conserved. Include are three possible formation processes, theorized properties, and three way they might eventually be detected. (DS)
International Nuclear Information System (INIS)
Ahmed, Mainuddin
2005-01-01
A new solution of Einstein equation in general relativity is found. This solution solves an outstanding problem of thermodynamics and black hole physics. Also this work appears to conclude the interpretation of NUT spacetime. (author)
International Nuclear Information System (INIS)
Hacisalihoglu, G.; Eliyakut, F.; Anwari, M.A.; Ataman, O.Y.; Balkas, T.I.; Tuncel, G.; Olmez, I.
1991-01-01
Shipboard, high volume air particulate samples were collected from the Black Sea atmosphere and analyzed by instrumental neutron activation analysis, atomic absorption spectrophotometry and ion chromatography for about 40 elements and ions. Concentrations of elements in the eastern and western parts of the Black Sea are different at the 95% confidence level, with lower concentrations in the eastern Black Sea. Back-trajectories and concentrations of elements in trajectory groups show that Europe accounts for more than 70% of the anthropogenic elements in the atmosphere. The average sulfate concentration was 7 μg/m 3 , which is comparable with rural sulfate levels in western Europe. Fluxes of elements from the atmosphere to the Black Sea are in good agreement with the results of similar flux calculations for other regions
Directory of Open Access Journals (Sweden)
Loretta I. Winters
2012-01-01
Full Text Available This article examines the relative importance of race and socioeconomic status (SES in determining whether Black and White teenagers report having ever been pregnant. Data gathered from 1999 to 2006 by the National Center for Health Statistics of the Center for Disease Control and Prevention included 1,580 Black and White females aged 15 to 19 years. Results supported the effects of race and SES, with SES having the stronger effect. However, the effects of race and SES differ when controlling for the state of the economy. No difference between Blacks and Whites was found during better economic times. During 2003-2004, the period of greatest economic stress, race was determined to be the only predictor of teenage pregnancy. In particular, during 2005-2006, the reduction in pregnancy rates for Black minors (15-17 fell below those for White minors within their respective SES categories. Policy implications are discussed in light of these findings.
International Nuclear Information System (INIS)
Bekenstein, J.D.
1980-01-01
Including black holes in the scheme of thermodynamics has disclosed a deep-seated connection between gravitation, heat and the quantum that may lead us to a synthesis of the corresponding branches of physics
International Nuclear Information System (INIS)
Sexl, R.; Sexl, H.
1975-01-01
The physical arguments and problems of relativistic astrophysics are presented in a correct way, but without any higher mathematics. The book is addressed to teachers, experimental physicists, and others with a basic knowledge covering an introductory lecture in physics. The issues dealt with are: fundamentals of general relativity, classical tests of general relativity, curved space-time, stars and planets, pulsars, gravitational collapse and black holes, the search for black holes, gravitational waves, cosmology, cosmogony, and the early universe. (BJ/AK) [de
de Wit, Bernard
2005-01-01
The effective action of $N=2$, $d=4$ supergravity is shown to acquire no quantum corrections in background metrics admitting super-covariantly constant spinors. In particular, these metrics include the Robinson-Bertotti metric (product of two 2-dimensional spaces of constant curvature) with all 8 supersymmetries unbroken. Another example is a set of arbitrary number of extreme Reissner-Nordstr\\"om black holes. These black holes break 4 of 8 supersymmetries, leaving the other 4 unbroken. We ha...
Emparan, Roberto; Figueras, Pau; Martinez, Marina
2014-01-01
We study six-dimensional rotating black holes with bumpy horizons: these are topologically spherical, but the sizes of symmetric cycles on the horizon vary non-monotonically with the polar angle. We construct them numerically for the first three bumpy families, and follow them in solution space until they approach critical solutions with localized singularities on the horizon. We find strong evidence of the conical structures that have been conjectured to mediate the transitions to black ring...
Adair, C.; Burt, Ramsay, 1953-
2016-01-01
British Dance: Black Routes re-examines the distinctive contributions made to British dance by dancers who are Black. Covering the period 1946 to the present, it presents a radical re-reading of dancers and their companies, placing their achievements within a broader historical, cultural and artistic context. The result of a two year research project, British Dance and the African Diaspora, led by editors Christy Adair and Ramsay Burt, the collection looks at artists working with contempor...
Black Holes and Thermodynamics
Wald, Robert M.
1997-01-01
We review the remarkable relationship between the laws of black hole mechanics and the ordinary laws of thermodynamics. It is emphasized that - in analogy with the laws of thermodynamics - the validity the laws of black hole mechanics does not appear to depend upon the details of the underlying dynamical theory (i.e., upon the particular field equations of general relativity). It also is emphasized that a number of unresolved issues arise in ``ordinary thermodynamics'' in the context of gener...
Energy Technology Data Exchange (ETDEWEB)
NONE
2002-02-01
Belief in the existence of black holes is the ultimate act of faith for a physicist. First suggested by the English clergyman John Michell in the year 1784, the gravitational pull of a black hole is so strong that nothing - not even light - can escape. Gravity might be the weakest of the fundamental forces but black-hole physics is not for the faint-hearted. Black holes present obvious problems for would-be observers because they cannot, by definition, be seen with conventional telescopes - although before the end of the decade gravitational-wave detectors should be able to study collisions between black holes. Until then astronomers can only infer the existence of a black hole from its gravitational influence on other matter, or from the X-rays emitted by gas and dust as they are dragged into the black hole. However, once this material passes through the 'event horizon' that surrounds the black hole, we will never see it again - not even with X-ray specs. Despite these observational problems, most physicists and astronomers believe that black holes do exist. Small black holes a few kilometres across are thought to form when stars weighing more than about two solar masses collapse under the weight of their own gravity, while supermassive black holes weighing millions of solar masses appear to be present at the centre of most galaxies. Moreover, some brave physicists have proposed ways to make black holes - or at least event horizons - in the laboratory. The basic idea behind these 'artificial black holes' is not to compress a large amount of mass into a small volume, but to reduce the speed of light in a moving medium to less than the speed of the medium and so create an event horizon. The parallels with real black holes are not exact but the experiments could shed new light on a variety of phenomena. The first challenge, however, is to get money for the research. One year on from a high-profile meeting on artificial black holes in London, for
Centrella, Joan
2012-01-01
The final merger of two black holes is expected to be the strongest source of gravitational waves for both ground-based detectors such as LIGO and VIRGO, as well as future. space-based detectors. Since the merger takes place in the regime of strong dynamical gravity, computing the resulting gravitational waveforms requires solving the full Einstein equations of general relativity on a computer. For many years, numerical codes designed to simulate black hole mergers were plagued by a host of instabilities. However, recent breakthroughs have conquered these instabilities and opened up this field dramatically. This talk will focus on.the resulting 'gold rush' of new results that is revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, testing general relativity, and astrophysics
Black hole gravitohydromagnetics
Punsly, Brian
2008-01-01
Black hole gravitohydromagnetics (GHM) is developed from the rudiments to the frontiers of research in this book. GHM describes plasma interactions that combine the effects of gravity and a strong magnetic field, in the vicinity (ergosphere) of a rapidly rotating black hole. This topic was created in response to the astrophysical quest to understand the central engines of radio loud extragalactic radio sources. The theory describes a "torsional tug of war" between rotating ergospheric plasma and the distant asymptotic plasma that extracts the rotational inertia of the black hole. The recoil from the struggle between electromagnetic and gravitational forces near the event horizon is manifested as a powerful pair of magnetized particle beams (jets) that are ejected at nearly the speed of light. These bipolar jets feed large-scale magnetized plasmoids on scales as large as millions of light years (the radio lobes of extragalactic radio sources). This interaction can initiate jets that transport energy fluxes exc...
Yang, Huan; Zimmerman, Aaron; Lehner, Luis
2015-02-27
We demonstrate that rapidly spinning black holes can display a new type of nonlinear parametric instability-which is triggered above a certain perturbation amplitude threshold-akin to the onset of turbulence, with possibly observable consequences. This instability transfers from higher temporal and azimuthal spatial frequencies to lower frequencies-a phenomenon reminiscent of the inverse cascade displayed by (2+1)-dimensional fluids. Our finding provides evidence for the onset of transitory turbulence in astrophysical black holes and predicts observable signatures in black hole binaries with high spins. Furthermore, it gives a gravitational description of this behavior which, through the fluid-gravity duality, can potentially shed new light on the remarkable phenomena of turbulence in fluids.
Aghaei Abchouyeh, Maryam; Mirza, Behrouz; Karimi Takrami, Moein; Younesizadeh, Younes
2018-05-01
We propose a correspondence between an Anyon Van der Waals fluid and a (2 + 1) dimensional AdS black hole. Anyons are particles with intermediate statistics that interpolates between a Fermi-Dirac statistics and a Bose-Einstein one. A parameter α (0 quasi Fermi-Dirac statistics for α >αc, but a quasi Bose-Einstein statistics for α quasi Bose-Einstein statistics. For α >αc and a range of values of the cosmological constant, there is, however, no event horizon so there is no black hole solution. Thus, for these values of cosmological constants, the AdS Anyon Van der Waals black holes have only quasi Bose-Einstein statistics.
Energy Technology Data Exchange (ETDEWEB)
Leonhardt, Ulf [School of Physics and Astronomy, University of St. Andrews (United Kingdom)
2001-02-01
In modern physics, the unification of gravity and quantum mechanics remains a mystery. Gravity rules the macroscopic world of planets, stars and galaxies, while quantum mechanics governs the micro-cosmos of atoms, light quanta and elementary particles. However, cosmologists believe that these two disparate worlds may meet at the edges of black holes. Now Luis Garay, James Anglin, Ignacio Cirac and Peter Zoller at the University of Innsbruck in Austria have proposed a realistic way to make an artificial 'sonic' black hole in a tabletop experiment (L J Garay et al. 2000 Phys. Rev. Lett. 85 4643). In the February issue of Physics World, Ulf Leonhardt of the School of Physics and Astronomy, University of St. Andrews, UK, explains how the simulated black holes work. (U.K.)
International Nuclear Information System (INIS)
Joshi, Pankaj S.; Narayan, Ramesh
2016-01-01
We propose here that the well-known black hole paradoxes such as the information loss and teleological nature of the event horizon are restricted to a particular idealized case, which is the homogeneous dust collapse model. In this case, the event horizon, which defines the boundary of the black hole, forms initially, and the singularity in the interior of the black hole at a later time. We show that, in contrast, gravitational collapse from physically more realistic initial conditions typically leads to the scenario in which the event horizon and space-time singularity form simultaneously. We point out that this apparently simple modification can mitigate the causality and teleological paradoxes, and also lends support to two recently suggested solutions to the information paradox, namely, the ‘firewall’ and ‘classical chaos’ proposals. (paper)
Furmann, John M.
2003-03-01
Black holes are difficult to study because they emit no light. To overcome this obstacle, scientists are trying to recreate a black hole in the laboratory. The article gives an overview of the theories of Einstein and Hawking as they pertain to the construction of the Large Hadron Collider (LHC) near Geneva, Switzerland, scheduled for completion in 2006. The LHC will create two beams of protons traveling in opposing directions that will collide and create a plethora of scattered elementary particles. Protons traveling in opposite directions at very high velocities may create particles that come close enough to each other to feel their compacted higher dimensions and create a mega force of gravity that can create tiny laboratory-sized black holes for fractions of a second. The experiments carried out with LHC will be used to test modern string theory and relativity.
International Nuclear Information System (INIS)
Lyutikov, Maxim; McKinney, Jonathan C.
2011-01-01
The 'no-hair' theorem, a key result in general relativity, states that an isolated black hole is defined by only three parameters: mass, angular momentum, and electric charge; this asymptotic state is reached on a light-crossing time scale. We find that the no-hair theorem is not formally applicable for black holes formed from the collapse of a rotating neutron star. Rotating neutron stars can self-produce particles via vacuum breakdown forming a highly conducting plasma magnetosphere such that magnetic field lines are effectively ''frozen in'' the star both before and during collapse. In the limit of no resistivity, this introduces a topological constraint which prohibits the magnetic field from sliding off the newly-formed event horizon. As a result, during collapse of a neutron star into a black hole, the latter conserves the number of magnetic flux tubes N B =eΦ ∞ /(πc(ℎ/2π)), where Φ ∞ ≅2π 2 B NS R NS 3 /(P NS c) is the initial magnetic flux through the hemispheres of the progenitor and out to infinity. We test this theoretical result via 3-dimensional general relativistic plasma simulations of rotating black holes that start with a neutron star dipole magnetic field with no currents initially present outside the event horizon. The black hole's magnetosphere subsequently relaxes to the split-monopole magnetic field geometry with self-generated currents outside the event horizon. The dissipation of the resulting equatorial current sheet leads to a slow loss of the anchored flux tubes, a process that balds the black hole on long resistive time scales rather than the short light-crossing time scales expected from the vacuum no-hair theorem.
Modeling black hole evaporation
Fabbri, Alessandro
2005-01-01
The scope of this book is two-fold: the first part gives a fully detailed and pedagogical presentation of the Hawking effect and its physical implications, and the second discusses the backreaction problem, especially in connection with exactly solvable semiclassical models that describe analytically the black hole evaporation process. The book aims to establish a link between the general relativistic viewpoint on black hole evaporation and the new CFT-type approaches to the subject. The detailed discussion on backreaction effects is also extremely valuable.
Characterizing Black Hole Mergers
Baker, John; Boggs, William Darian; Kelly, Bernard
2010-01-01
Binary black hole mergers are a promising source of gravitational waves for interferometric gravitational wave detectors. Recent advances in numerical relativity have revealed the predictions of General Relativity for the strong burst of radiation generated in the final moments of binary coalescence. We explore features in the merger radiation which characterize the final moments of merger and ringdown. Interpreting the waveforms in terms of an rotating implicit radiation source allows a unified phenomenological description of the system from inspiral through ringdown. Common features in the waveforms allow quantitative description of the merger signal which may provide insights for observations large-mass black hole binaries.
Better Physician's 'Black Bags'
1976-01-01
The "black bag" is outgrowth of astronaut monitoring technology from NASA's Johnson Space Center. Technically known as the portable medical status system, a highly advanced physician's "black bag" weighs less than 30 pounds, yet contains equipment for monitoring and recording vital signs, electrocardiograms, and electroencephalograms. Liquid crystal displays are used to present 15 digits of data simultaneously for long periods of time without excessive use of battery power. Single printed circuit card contains all circuitry required to measure and display vital signs such as heart and respiration rate, temperature, and blood pressure.
DEFF Research Database (Denmark)
Højer, Henrik
2016-01-01
Netflix’ kommende serie om den sorte Marvel-helt Luke Cage lander snart – midt i de aktuelle racekonflikter i USA. I GIF-anatomien "Bulletproof Black Man" sætter Henrik Højer serien ind i dens amerikanske kontekst.......Netflix’ kommende serie om den sorte Marvel-helt Luke Cage lander snart – midt i de aktuelle racekonflikter i USA. I GIF-anatomien "Bulletproof Black Man" sætter Henrik Højer serien ind i dens amerikanske kontekst....
Bena, Iosif; Chowdhury, Borun D.; de Boer, Jan; El-Showk, Sheer; Shigemori, Masaki
2011-01-01
We find a family of novel supersymmetric phases of the D1-D5 CFT, which in certain ranges of charges have more entropy than all known ensembles. We also find bulk BPS configurations that exist in the same range of parameters as these phases, and have more entropy than a BMPV black hole; they can be thought of as coming from a BMPV black hole shedding a "hair" condensate outside of the horizon. The entropy of the bulk configurations is smaller than that of the CFT phases, which indicates that ...
Good, Michael R. R.; Ong, Yen Chin
2015-02-01
A (3 +1 )-dimensional asymptotically flat Kerr black hole angular speed Ω+ can be used to define an effective spring constant, k =m Ω+2. Its maximum value is the Schwarzschild surface gravity, k =κ , which rapidly weakens as the black hole spins down and the temperature increases. The Hawking temperature is expressed in terms of the spring constant: 2 π T =κ -k . Hooke's law, in the extremal limit, provides the force F =1 /4 , which is consistent with the conjecture of maximum force in general relativity.
Aarseth, S. J.
2008-05-01
We describe efforts over the last six years to implement regularization methods suitable for studying one or more interacting black holes by direct N-body simulations. Three different methods have been adapted to large-N systems: (i) Time-Transformed Leapfrog, (ii) Wheel-Spoke, and (iii) Algorithmic Regularization. These methods have been tried out with some success on GRAPE-type computers. Special emphasis has also been devoted to including post-Newtonian terms, with application to moderately massive black holes in stellar clusters. Some examples of simulations leading to coalescence by gravitational radiation will be presented to illustrate the practical usefulness of such methods.
International Nuclear Information System (INIS)
Futterman, J.A.H.; Handler, F.A.; Matzner, R.A.
1987-01-01
This book provides a comprehensive treatment of the propagation of waves in the presence of black holes. While emphasizing intuitive physical thinking in their treatment of the techniques of analysis of scattering, the authors also include chapters on the rigorous mathematical development of the subject. Introducing the concepts of scattering by considering the simplest, scalar wave case of scattering by a spherical (Schwarzschild) black hole, the book then develops the formalism of spin weighted spheroidal harmonics and of plane wave representations for neutrino, electromagnetic, and gravitational scattering. Details and results of numerical computations are given. The techniques involved have important applications (references are given) in acoustical and radar imaging
Hawking, Stephen W.
1995-01-01
One would expect spacetime to have a foam-like structure on the Planck scale with a very high topology. If spacetime is simply connected (which is assumed in this paper), the non-trivial homology occurs in dimension two, and spacetime can be regarded as being essentially the topological sum of $S^2\\times S^2$ and $K3$ bubbles. Comparison with the instantons for pair creation of black holes shows that the $S^2\\times S^2$ bubbles can be interpreted as closed loops of virtual black holes. It is ...
Hennigar, Robie A; Mann, Robert B; Tjoa, Erickson
2017-01-13
We present what we believe is the first example of a "λ-line" phase transition in black hole thermodynamics. This is a line of (continuous) second order phase transitions which in the case of liquid ^{4}He marks the onset of superfluidity. The phase transition occurs for a class of asymptotically anti-de Sitter hairy black holes in Lovelock gravity where a real scalar field is conformally coupled to gravity. We discuss the origin of this phase transition and outline the circumstances under which it (or generalizations of it) could occur.
International Nuclear Information System (INIS)
Susskind, L.; Griffin, P.
1994-01-01
A light-front renormalization group analysis is applied to study matter which falls into massive black holes, and the related problem of matter with transplankian energies. One finds that the rate of matter spreading over the black hole's horizon unexpectedly saturates the causality bound. This is related to the transverse growth behavior of transplankian particles as their longitudinal momentum increases. This growth behavior suggests a natural mechanism to implement 't Hooft's scenario that the universe is an image of data stored on a 2 + 1 dimensional hologram-like projection
Black Musicians Leading the Way.
Music Educators Journal, 1982
1982-01-01
Describes the careers and musical achievements of Blacks who were forerunners in jazz, blues, gospel, music, spirituals, band music, classical music, ragtime, and opera. The list was compiled to provide teachers with historical background information for "Black History Month." (AM)
Black holes and quantum mechanics
Wilczek, Frank
1995-01-01
1. Qualitative introduction to black holes : classical, quantum2. Model black holes and model collapse process: The Schwarzschild and Reissner-Nordstrom metrics, The Oppenheimer-Volkov collapse scenario3. Mode mixing4. From mode mixing to radiance.
Black Sea Bass genetic connectivity
National Oceanic and Atmospheric Administration, Department of Commerce — Microsatellite analysis of black sea bass was undertaken to determine magnitude and direction of mixing of black seabass across the Hatteras boundary, as well as...
Quantum aspects of black holes
2015-01-01
Beginning with an overview of the theory of black holes by the editor, this book presents a collection of ten chapters by leading physicists dealing with the variety of quantum mechanical and quantum gravitational effects pertinent to black holes. The contributions address topics such as Hawking radiation, the thermodynamics of black holes, the information paradox and firewalls, Monsters, primordial black holes, self-gravitating Bose-Einstein condensates, the formation of small black holes in high energetic collisions of particles, minimal length effects in black holes and small black holes at the Large Hadron Collider. Viewed as a whole the collection provides stimulating reading for researchers and graduate students seeking a summary of the quantum features of black holes.
Energy Technology Data Exchange (ETDEWEB)
Anabalón, Andrés, E-mail: andres.anabalon-at@uai.cl [Departamento de Ciencias, Facultad de Artes Liberales y Facultad de Ingeniería y Ciencias, Universidad Adolfo Ibáñez, Viña del Mar (Chile); Astefanesei, Dumitru [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso (Chile)
2015-03-26
We review the existence of exact hairy black holes in asymptotically flat, anti-de Sitter and de Sitter space-times. We briefly discuss the issue of stability and the charging of the black holes with a Maxwell field.
Black Holes in Higher Dimensions
Directory of Open Access Journals (Sweden)
Reall Harvey S.
2008-09-01
Full Text Available We review black-hole solutions of higher-dimensional vacuum gravity and higher-dimensional supergravity theories. The discussion of vacuum gravity is pedagogical, with detailed reviews of Myers–Perry solutions, black rings, and solution-generating techniques. We discuss black-hole solutions of maximal supergravity theories, including black holes in anti-de Sitter space. General results and open problems are discussed throughout.
Energy Technology Data Exchange (ETDEWEB)
Chamseddine, Ali H. [American University of Beirut, Physics Department, Beirut (Lebanon); I.H.E.S., Bures-sur-Yvette (France); Mukhanov, Viatcheslav [Niels Bohr Institute, Niels Bohr International Academy, Copenhagen (Denmark); Ludwig-Maximilians University, Theoretical Physics, Munich (Germany); MPI for Physics, Munich (Germany)
2017-03-15
We consider the Schwarzschild black hole and show how, in a theory with limiting curvature, the physical singularity ''inside it'' is removed. The resulting spacetime is geodesically complete. The internal structure of this nonsingular black hole is analogous to Russian nesting dolls. Namely, after falling into the black hole of radius r{sub g}, an observer, instead of being destroyed at the singularity, gets for a short time into the region with limiting curvature. After that he re-emerges in the near horizon region of a spacetime described by the Schwarzschild metric of a gravitational radius proportional to r{sub g}{sup 1/3}. In the next cycle, after passing the limiting curvature, the observer finds himself within a black hole of even smaller radius proportional to r{sub g}{sup 1/9}, and so on. Finally after a few cycles he will end up in the spacetime where he remains forever at limiting curvature. (orig.)
Lewis-McCoy, R. L'Heureux
2018-01-01
This article explores the range of experiences and meanings of Black life in suburban space. Drawing from educational, historical, and sociological literatures, I argue that an underconsideration of suburban space has left many portraits of educational inequality incomplete. The article outlines the emergence of American suburbs and the formation…
African Journals Online (AJOL)
Keywords: Black Cumin Seed, Co-pressing, Screw Speed, Oxidative Stability, Niger Seed Oil ... against oxidation resulting in rapid development of .... The machine ... apparatus (Metrohm, Herisau, model Switzerland) at .... present study indicates the need to optimize SS for ..... Mathematical simulation of an oilseed press.
International Nuclear Information System (INIS)
Zeldovich, Ya.; Novikov, I.; Starobinskij, A.
1978-01-01
The theory is explained of the origination of white holes as a dual phenomenon with regard to the formation of black holes. Theoretically it is possible to derive the white hole by changing the sign of time in solving the general theory of relativity equation implying the black hole. The white hole represents the amount of particles formed in the vicinity of a singularity. For a distant observer, matter composed of these particles expands and the outer boundaries of this matter approach from the inside the gravitational radius Rsub(r). At t>>Rsub(r)/c all radiation or expulsion of matter terminates. For the outside observer the white hole exists for an unlimited length of time. In fact, however, it acquires the properties of a black hole and all processes in it cease. The qualitative difference between a white hole and a black hole is in that a white hole is formed as the result of an inner quantum explosion from the singularity to the gravitational radius and not as the result of a gravitational collapse, i.e., the shrinkage of diluted matter towards the gravitational radius. (J.B.)
Energy Technology Data Exchange (ETDEWEB)
Zeldovich, Ya; Novikov, I; Starobinskii, A
1978-07-01
The theory is explained of the origination of white holes as a dual phenomenon with regard to the formation of black holes. Theoretically it is possible to derive the white hole by changing the sign of time in solving the general theory of relativity equation implying the black hole. The white hole represents the amount of particles formed in the vicinity of a singularity. For a distant observer, matter composed of these particles expands and the outer boundaries of this matter approach from the inside the gravitational radius R/sub r/. At t>>R/sub r//c all radiation or expulsion of matter terminates. For the outside observer the white hole exists for an unlimited length of time. In fact, however, it acquires the properties of a black hole and all processes in it cease. The qualitative difference between a white hole and a black hole is in that a white hole is formed as the result of an inner quantum explosion from the singularity to the gravitational radius and not as the result of a gravitational collapse, i.e., the shrinkage of diluted matter towards the gravitational radius.
Annotated black walnut literature
J. W. Van Sambeek
2006-01-01
Many of our publications on the establishment, management, and utilization of black walnut, butternut, and associated high-value hardwoods are printed in conference proceedings or scientific journals that are not readily available at most public libraries or on the internet. As Chair of the Education Committee, I have tried to summarize for you the relevant findings of...
Baker, John
2010-01-01
Among the fascinating phenomena predicted by General Relativity, Einstein's theory of gravity, black holes and gravitational waves, are particularly important in astronomy. Though once viewed as a mathematical oddity, black holes are now recognized as the central engines of many of astronomy's most energetic cataclysms. Gravitational waves, though weakly interacting with ordinary matter, may be observed with new gravitational wave telescopes, opening a new window to the universe. These observations promise a direct view of the strong gravitational dynamics involving dense, often dark objects, such as black holes. The most powerful of these events may be merger of two colliding black holes. Though dark, these mergers may briefly release more energy that all the stars in the visible universe, in gravitational waves. General relativity makes precise predictions for the gravitational-wave signatures of these events, predictions which we can now calculate with the aid of supercomputer simulations. These results provide a foundation for interpreting expect observations in the emerging field of gravitational wave astronomy.
Baskin, Wade; Runes, Richard N.
This dictionary is an encyclopedic survey of the cultural background and development of the black American, covering the basic issues, events, contributions and biographies germane to the subject. The author-compiler is Chairman of Classical Languages Department at Southeastern State College, Durant, Oklahoma. Richard Runes is practicing law as a…
Science Teacher, 2005
2005-01-01
Scientists using NASA's Swift satellite say they have found newborn black holes, just seconds old, in a confused state of existence. The holes are consuming material falling into them while somehow propelling other material away at great speeds. "First comes a blast of gamma rays followed by intense pulses of x-rays. The energies involved are much…
Energy Technology Data Exchange (ETDEWEB)
Pratt, R
1973-01-01
Statistics are given for the Australian black coal industry for 1970-3 (production, value, employment, wages and salaries, productivity, trade, stocks, consumption, export contracts, exploration, etc.). In less detail, world coal trade is reviewed and coke production is mentioned briefly. (LTN )
The Black Hole Firewall and Top-Down Constructions of AdS/CFT
Almheiri, Ahmed Eid Khamis Thani
In the first part of this dissertation we argue that the following statements cannot be all true: (i) Black hole formation and evaporation is a unitary process as viewed by external observers, (ii) Physics outside some microscopic distance away from the event horizon is described by local effective quantum field theory, (iii) A black hole is a quantum system with a finite number of states given by the exponential of the Bekenstein Hawking entropy, and (iv) An infalling observer's experience in the vicinity of the horizon is well described by local effective quantum field theory in the infalling reference frame. We argue that the most conservative resolution is that an infalling observer will see drastic violations of effective field theory far away from the singularity, and encounter high energy quanta, a firewall, just behind the black hole event horizon. We address counter proposals to the firewall which involve, in one way or another, radical modifications of quantum mechanics or locality, and argue that they are unsatisfactory in their current formulation. We conclude this part with an investigation into the existence of firewalls in the two dimensional Einstein-dilaton gravity model of CGHS. We find that black holes in such models do not develop firewalls, but rather evaporate down to form small mass remnants. We elaborate on why this is inevitable in two dimensions and argue against a similar conclusion in higher dimensions. In the second part of this dissertation we construct AdS2 and AdS3 magnetic brane solutions within the abelian truncations of AdS4 x orbifolded S7 and AdS5 x S5 supergravity. We find a class of supersymmetric solutions of the bulk theory to assure stability. We perform a preliminary analysis demonstrating the stability of some nonsupersymmetric embeddings. We identify the dual field theory and compare the thermal entropies across the duality. We end with an investigatation into the effects of backreaction on holography in AdS2. We study a
Australian black coal statistics 1990
Energy Technology Data Exchange (ETDEWEB)
1991-01-01
This second edition of Australian black coal statistics replaces the Joint Coal Board's publication 'Black coal in Australia'. It includes an expanded international coal trade supplement. Sections cover resources of black coal, coal supply and demand, coal production, employment and productivity of mines, export data, coal consumption and a directory of producers.
Uncovering Black Womanhood in Engineering
Gibson, Sheree L.; Espino, Michelle M.
2016-01-01
Despite the growing research that outlines the experiences of Blacks and women undergraduates in engineering, little is known about Black women in this field. The purpose of this qualitative study was to uncover how eight Black undergraduate women in engineering understood their race and gender identities in a culture that can be oppressive to…
Watchable Wildlife: The Black Bear
Lynn L. Rogers
1992-01-01
Black bears are the bears people most often encounter. Black bears live in forests over much of North America, unlike grizzlies that live only in Alaska, northern and western Canada, and the northern Rocky Mountains. This brochure presents the latest information on black bear life and how this species responds to an ever-increasing number of campers, hikers, and...
Schram, Sarah E; Willey, Andrea; Lee, Peter K; Bohjanen, Kimberly A; Warshaw, Erin M
2008-01-01
In black-spot poison ivy dermatitis, a black lacquerlike substance forms on the skin when poison ivy resin is exposed to air. Although the Toxicodendron group of plants is estimated to be the most common cause of allergic contact dermatitis in the United States, black-spot poison ivy dermatitis is relatively rare.
Queering Black Racial Identity Development
Johnson, Alandis A.; Quaye, Stephen John
2017-01-01
We used queer theory to encourage readers to think differently about previous theories about Black racial identity development. Queer theory facilitates new and deeper understandings of how Black people develop their racial identities, prompting more fluidity and nuance. Specifically, we present a queered model of Black racial identity development…
A Typology of Black Leadership.
Tryman, Donald L.
1977-01-01
A leadership typology is developed which describes the relationship of Black leadership styles to the Black masses. The role that such leadership plays in the political integration of Blacks as an ethnic group is analyzed. Four authority types are discussed: traditional brokerage, cultural nationalist, religious nationalist, and faddist…
Warped products and black holes
International Nuclear Information System (INIS)
Hong, Soon-Tae
2005-01-01
We apply the warped product space-time scheme to the Banados-Teitelboim-Zanelli black holes and the Reissner-Nordstroem-anti-de Sitter black hole to investigate their interior solutions in terms of warped products. It is shown that there exist no discontinuities of the Ricci and Einstein curvatures across event horizons of these black holes
Magnetohydrodynamics near a black hole
International Nuclear Information System (INIS)
Wilson, J.R.
1975-01-01
A numerical computer study of hydromagnetic flow near a black hole is presented. First, the equations of motion are developed to a form suitable for numerical computations. Second, the results of calculations describing the magnetic torques exerted by a rotating black hole on a surrounding magnetic plasma and the electric charge that is induced on the surface of the black hole are presented. (auth)
S-duality constraint on higher-derivative couplings
International Nuclear Information System (INIS)
Garousi, Mohammad R.
2014-01-01
The Riemann curvature correction to the type II supergravity at eight-derivative level in string frame is given as e"−"2"ϕ(t_8t_8R"4+(1/4)ϵ_8ϵ_8R"4). For constant dilaton, it has been extended in the literature to the S-duality invariant form by extending the dilaton factor in the Einstein frame to the non-holomorphic Eisenstein series. For non-constant dilaton, however, there are various couplings in the Einstein frame which are not consistent with the S-duality. By constructing the tensors t_2_n from Born-Infeld action, we include the appropriate Ricci and scalar curvatures as well as the dilaton couplings to make the above action to be consistent with the S-duality
S-duality constraint on higher-derivative couplings
Energy Technology Data Exchange (ETDEWEB)
Garousi, Mohammad R. [Department of Physics, Ferdowsi University of Mashhad,P.O. Box 1436, Mashhad (Iran, Islamic Republic of)
2014-05-22
The Riemann curvature correction to the type II supergravity at eight-derivative level in string frame is given as e{sup −2ϕ}(t{sub 8}t{sub 8}R{sup 4}+(1/4)ϵ{sub 8}ϵ{sub 8}R{sup 4}). For constant dilaton, it has been extended in the literature to the S-duality invariant form by extending the dilaton factor in the Einstein frame to the non-holomorphic Eisenstein series. For non-constant dilaton, however, there are various couplings in the Einstein frame which are not consistent with the S-duality. By constructing the tensors t{sub 2n} from Born-Infeld action, we include the appropriate Ricci and scalar curvatures as well as the dilaton couplings to make the above action to be consistent with the S-duality.
Black silicon with black bus-bar strings
DEFF Research Database (Denmark)
Davidsen, Rasmus Schmidt; Tang, Peter Torben; Mizushima, Io
2016-01-01
We present the combination of black silicon texturing and blackened bus-bar strings as a potential method for obtaining all-black solar panels, while using conventional, front-contacted solar cells. Black silicon was realized by mask-less reactive ion etching resulting in total, average reflectance...... below 0.5% across a 156x156 mm2 silicon wafer. Black bus-bars were realized by oxidized copper resulting in reflectance below 3% in the entire visible wavelength range. The combination of these two technologies may result in aesthetic, all-black panels based on conventional, front-contacted solar cells...
Looking for the invisible universe - Black matter, black energy, black holes
International Nuclear Information System (INIS)
Elbaz, David
2016-01-01
As the discovery of the expansion of the universe and of black holes put the study of cosmology into question again because it now refers to invisible things such as black holes, black energy and black matter, the author proposes an other view on the universe within such a context. He first discusses these three enigmas of black matter, black energy and black holes. In a second part, he addresses, discusses and comments five illusions: the Uranian illusion (questions of the existence of an anti-world, of black matter temperature), the Mercurian illusion (quantum gravity, the string theory), the Martian illusion (a patchwork universe, the illusion of the infinite), the cosmic Maya (the John Wheeler's cup, the holographic universe), and the narcissistic illusion
From binary black hole simulation to triple black hole simulation
International Nuclear Information System (INIS)
Bai Shan; Cao Zhoujian; Han, Wen-Biao; Lin, Chun-Yu; Yo, Hwei-Jang; Yu, Jui-Ping
2011-01-01
Black hole systems are among the most promising sources for a gravitational wave detection project. Now, China is planning to construct a space-based laser interferometric detector as a follow-on mission of LISA in the near future. Aiming to provide some theoretical support to this detection project on the numerical relativity side, we focus on black hole systems simulation in this work. Considering the globular galaxy, multiple black hole systems also likely to exist in our universe and play a role as a source for the gravitational wave detector we are considering. We will give a progress report in this paper on our black hole system simulation. More specifically, we will present triple black hole simulation together with binary black hole simulation. On triple black hole simulations, one novel perturbational method is proposed.
Statistical mechanics of black holes
International Nuclear Information System (INIS)
Harms, B.; Leblanc, Y.
1992-01-01
We analyze the statistical mechanics of a gas of neutral and charged black holes. The microcanonical ensemble is the only possible approach to this system, and the equilibrium configuration is the one for which most of the energy is carried by a single black hole. Schwarzschild black holes are found to obey the statistical bootstrap condition. In all cases, the microcanonical temperature is identical to the Hawking temperature of the most massive black hole in the gas. U(1) charges in general break the bootstrap property. The problems of black-hole decay and of quantum coherence are also addressed
Kao, Robert
2010-01-01
Get the most juice out of your BlackBerry handheld!. Feature-rich and complex, the BlackBerry is the number one smartphone in the corporate world is among the most popular handhelds for business users. This new and updated edition includes all the latest and greatest information on new and current BlackBerry mobile devices. Covering a range of valuable how-to topics, this helpful guide explores the BlackBerry's most useful features, techniques for getting the most out of your BlackBerry, and practical information about power usage.: Covers all aspects of the number one smartphone in the corpor
Energy Technology Data Exchange (ETDEWEB)
Bouhmadi-Lopez, Mariam; Cardoso, Vitor; Nerozzi, Andrea; Rocha, Jorge V, E-mail: mariam.bouhmadi@ist.utl.pt, E-mail: vitor.cardoso@ist.utl.pt, E-mail: andrea.nerozzi@ist.utl.pt, E-mail: jorge.v.rocha@ist.utl.pt [CENTRA, Department de Fisica, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049 Lisboa (Portugal)
2011-09-22
A possible process to destroy a black hole consists on throwing point particles with sufficiently large angular momentum into the black hole. In the case of Kerr black holes, it was shown by Wald that particles with dangerously large angular momentum are simply not captured by the hole, and thus the event horizon is not destroyed. Here we reconsider this gedanken experiment for black holes in higher dimensions. We show that this particular way of destroying a black hole does not succeed and that Cosmic Censorship is preserved.
Internal structure of black holes
International Nuclear Information System (INIS)
Cvetic, Mirjam
2013-01-01
Full text: We review recent progress that sheds light on the internal structure of general black holes. We first summarize properties of general multi-charged rotating black holes both in four and five dimensions. We show that the asymptotic boundary conditions of these general asymptotically flat black holes can be modified such that a conformal symmetry emerges. These subtracted geometries preserve the thermodynamic properties of the original black holes and are of the Lifshitz type, thus describing 'a black hole in the asymptotically conical box'. Recent efforts employ solution generating techniques to construct interpolating geometries between the original black hole and their subtracted geometries. Upon lift to one dimension higher, these geometries lift to AdS 3 times a sphere, and thus provide a microscopic interpretation of the black hole entropy in terms of dual two-dimensional conformal field theory. (author)
Caged black holes: Black holes in compactified spacetimes. I. Theory
International Nuclear Information System (INIS)
Kol, Barak; Sorkin, Evgeny; Piran, Tsvi
2004-01-01
In backgrounds with compact dimensions there may exist several phases of black objects including a black hole and a black string. The phase transition between them raises questions and touches on fundamental issues such as topology change, uniqueness, and cosmic censorship. No analytic solution is known for the black hole, and moreover one can expect approximate solutions only for very small black holes, while phase transition physics happens when the black hole is large. Hence we turn to numerical solutions. Here some theoretical background to the numerical analysis is given, while the results will appear in a subsequent paper. The goals for a numerical analysis are set. The scalar charge and tension along the compact dimension are defined and used as improved order parameters which put both the black hole and the black string at finite values on the phase diagram. The predictions for small black holes are presented. The differential and the integrated forms of the first law are derived, and the latter (Smarr's formula) can be used to estimate the 'overall numerical error'. Field asymptotics and expressions for physical quantities in terms of the numerical values are supplied. The techniques include the 'method of equivalent charges', free energy, dimensional reduction, and analytic perturbation for small black holes
Energy Technology Data Exchange (ETDEWEB)
Bender, P. [Univ. of Colorado, Boulder, CO (United States); Bloom, E. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Cominsky, L. [Sonoma State Univ., Rohnert Park, CA (United States). Dept. of Physics and Astronomy] [and others
1995-07-01
Black-hole astrophysics is not just the investigation of yet another, even if extremely remarkable type of celestial body, but a test of the correctness of the understanding of the very properties of space and time in very strong gravitational fields. Physicists` excitement at this new prospect for testing theories of fundamental processes is matched by that of astronomers at the possibility to discover and study a new and dramatically different kind of astronomical object. Here the authors review the currently known ways that black holes can be identified by their effects on their neighborhood--since, of course, the hole itself does not yield any direct evidence of its existence or information about its properties. The two most important empirical considerations are determination of masses, or lower limits thereof, of unseen companions in binary star systems, and measurement of luminosity fluctuations on very short time scales.
Polchinski, Joseph
2015-04-01
Our modern understanding of space, time, matter, and even reality itself arose from the three great revolutions of the early twentieth century: special relativity, general relativity, and quantum mechanics. But a century later, this work is unfinished. Many deep connections have been discovered, but the full form of a unified theory incorporating all three principles is not known. Thought experiments and paradoxes have often played a key role in figuring out how to fit theories together. For the unification of general relativity and quantum mechanics, black holes have been an important arena. I will talk about the quantum mechanics of black holes, the information paradox, and the latest version of this paradox, the firewall. The firewall points to a conflict between our current theories of spacetime and of quantum mechanics. It may lead to a new understanding of how these are connected, perhaps based on quantum entanglement.
Directory of Open Access Journals (Sweden)
Barry Chevannes
1992-07-01
Full Text Available [First paragraph] The Rastafarians: sounds of cultural dissonance [revised and updated editionj. LEONARD E. BARRETT, SR. Boston: Beacon Press, 1988. xviii + 302 pp. (Paper US$ 11.95 Rasta and resistance: from Marcus Garvey to Walter Rodney. HORACE CAMPBELL. Trenton NJ: Africa World Press, 1987. xiii + 236 pp. (Cloth US$32.95, Paper US$ 10.95 Garvey's children: the legacy of Marcus Garvey. TONY SEWELL. London: Macmillan Caribbean, 1990. 128 pp. (Paper £ 17.95 The central theme linking these three titles is the evolution of a black identity among English-speaking Caribbean peoples, in particular Jamaicans. Consequently all three authors cover the two most important historical phenomena in Caribbean black nationalism, namely Garveyism and Rastafari, one focusing on the former and the other two focusing on the latter.
International Nuclear Information System (INIS)
Boslough, J.
1985-01-01
This book is about the life and work of Stephen Hawking. It traces the development of his theories about the universe and particularly black holes, in a biographical context. Hawking's lecture 'Is the end in sight for theoretical physics' is presented as an appendix. In this, he discusses the possibility of achieving a complete, consistent and unified theory of the physical interactions which would describe all possible observations. (U.K.)
Roldán-Molina, A.; Nunez, A.S.; Duine, R. A.
2017-01-01
We show that the interaction between spin-polarized current and magnetization dynamics can be used to implement black-hole and white-hole horizons for magnons - the quanta of oscillations in the magnetization direction in magnets. We consider three different systems: easy-plane ferromagnetic metals, isotropic antiferromagnetic metals, and easy-plane magnetic insulators. Based on available experimental data, we estimate that the Hawking temperature can be as large as 1 K. We comment on the imp...
Black Friday = Broget Branding?
DEFF Research Database (Denmark)
Hansen, Heidi
2015-01-01
? Essensen ved Black Friday er lave priser, og det er der ved første øjekast ikke mange brandingmuligheder forbundet ved, hvis man forstår branding som en måde at skabe ekstra værdi omkring sit produkt eller sin virksomhed. Som brand bliver man dog alligevel nødt til at forholde sig til konceptet, da det er...
1989-01-01
Difficulties with this romantic concept developed, however, when General Faidherbe began to expand French control into the Senegalese hinterland. He was...and his German 45 France in Black Africa friends to gain greater control of the AOF.6 The tragi- comedy ended with the 1942 Allied landings in North...service]). Trinquier’s own stay in Africa was short-lived. Belgian resistance to a French invasion of their turf was fierce. Trinquier’s romantic
International Nuclear Information System (INIS)
Drevet, J.F.
2008-01-01
In this month's European column, Jean-Francois Drevet examines the issues that arise for Europe from the Black Sea region. The Black Sea is increasingly becoming a crucial place of transit for hydrocarbon imports from the Caspian and Russia into the European Union. The considerable increase in this traffic raises both environmental problems (the risk of oil slicks) and issues of security of supply, on account of the economic and political fragility of some of the bordering or neighbouring states (Ukraine, Georgia, Armenia, Azerbaijan, Russia/Chechnya etc.). This is why, as Jean-Francois Drevet stresses, the European Union has been trying since the mid-1990's to claim a role in the management of the affairs of the region. With two bordering states (Rumania and Bulgaria) joining the EU in 2007, cooperation in the Black Sea has become a priority within the framework of the European Neighbourhood Policy, and this column delineates a number of the obstacles that still have to be surmounted. (author)
Black silicon solar cells with black bus-bar strings
DEFF Research Database (Denmark)
Davidsen, Rasmus Schmidt; Tang, Peter Torben; Mizushima, Io
2016-01-01
We present the combination of black silicon texturing and blackened bus-bar strings as a potential method for obtaining all-black solar panels, while using conventional, front-contacted solar cells. Black silicon was realized by maskless reactive ion etching resulting in total, average reflectance...... below 0.5% across a 156x156 mm2 silicon wafer. Four different methods to obtain blackened bus-bar strings were compared with respect to reflectance, and two of these methods (i.e., oxidized copper and etched solder) were used to fabricate functional allblack solar 9-cell panels. The black bus-bars (e.......g., by oxidized copper) have a reflectance below 3% in the entire visible wavelength range. The combination of black silicon cells and blackened bus-bars results in aesthetic, all-black panels based on conventional, front-contacted solar cells without compromising efficiency....
Black Hole Area Quantization rule from Black Hole Mass Fluctuations
Schiffer, Marcelo
2016-01-01
We calculate the black hole mass distribution function that follows from the random emission of quanta by Hawking radiation and with this function we calculate the black hole mass fluctuation. From a complete different perspective we regard the black hole as quantum mechanical system with a quantized event horizon area and transition probabilities among the various energy levels and then calculate the mass dispersion. It turns out that there is a perfect agreement between the statistical and ...
Emanuel, K.; Lin, N.
2012-12-01
Virtually all assessments of tropical cyclone risk are based on historical records, which are limited to a few hundred years at most. Yet stronger TCs may occur in the future and at places that have not been affected historically. Such events lie outside the realm of historically based expectations and may have extreme impacts. Their occurrences are also often made explainable after the fact (e.g., Hurricane Katrina). We nickname such potential future TCs, characterized by rarity, extreme impact, and retrospective predictability, "black swans" (Nassim Nicholas Taleb, 2007). As, by definition, black swan TCs have yet to happen, statistical methods that solely rely on historical track data cannot predict their occurrence. Global climate models lack the capability to predict intense storms, even with a resolution as high as 14 km (Emanuel et al. 2010). Also, most dynamic downscaling methods (e.g., Bender et al. 2010) are still limited in horizontal resolution and are too expensive to implement to generate enough events to include rare ones. In this study, we apply a simpler statistical/deterministic hurricane model (Emanuel et al. 2006) to simulate large numbers of synthetic storms under a given (observed or projected) climate condition. The method has been shown to generate realistic extremes in various basins (Emanuel et al. 2008 and 2010). We also apply a hydrodynamic model (ADCIRC; Luettich et al. 1992) to simulate the storm surges generated by these storms. We then search for black swan TCs, in terms of the joint wind and surge damage potential, in the generated large databases. Heavy rainfall is another important TC hazard and will be considered in a future study. We focus on three areas: Tampa Bay in the U.S., the Persian Gulf, and Darwin in Australia. Tampa Bay is highly vulnerable to storm surge as it is surrounded by shallow water and low-lying lands, much of which may be inundated by a storm tide of 6 m. High surges are generated by storms with a broad
2012-11-26
... Bear Hydro Partners, LLC and Black Bear Development Holdings, LLC and Black Bear SO, LLC; Notice of..., 2012, Black Bear Hydro Partners, LLC, sole licensee (transferor) and Black Bear Development Holdings, LLC and Black Bear SO, LLC (transferees) filed an application for the partial the transfer of licenses...
Quantum effects in black holes
International Nuclear Information System (INIS)
Frolov, V.P.
1979-01-01
A strict definition of black holes is presented and some properties with regard to their mass are enumerated. The Hawking quantum effect - the effect of vacuum instability in the black hole gravitational field, as a result of shich the black hole radiates as a heated body is analyzed. It is shown that in order to obtain results on the black hole radiation it is sufficient to predetermine the in-vacuum state at a time moment in the past, when the collapsing body has a large size, and its gravitational field can be neglected. The causes and the place of particle production by the black hole, and also the space-time inside the black hole, are considered
Particle creation by black holes
International Nuclear Information System (INIS)
Hawking, S.W.
1975-01-01
In the classical theory black holes can only absorb and not emit particles. However it is shown that quantum mechanical effects cause black holes to create and emit particles. This thermal emission leads to a slow decrease in the mass of the black hole and to its eventual disappearance: any primordial black hole of mass less than about 10 15 g would have evaporated by now. Although these quantum effects violate the classical law that the area of the event horizon of a black hole cannot decrease, there remains a Generalized Second Law: S + 1/4 A never decreases where S is the entropy of matter outside black holes and A is the sum of the surface areas of the event horizons. This shows that gravitational collapse converts the baryons and leptons in the collapsing body into entropy. It is tempting to speculate that this might be the reason why the Universe contains so much entropy per baryon. (orig.) [de
Dvali, Gia
2013-01-01
According to the standard view classically black holes carry no hair, whereas quantum hair is at best exponentially weak. We show that suppression of hair is an artifact of the semi-classical treatment and that in the quantum picture hair appears as an inverse mass-square effect. Such hair is predicted in the microscopic quantum description in which a black hole represents a self-sustained leaky Bose-condensate of N soft gravitons. In this picture the Hawking radiation is the quantum depletion of the condensate. Within this picture we show that quantum black hole physics is fully compatible with continuous global symmetries and that global hair appears with the strength B/N, where B is the global charge swallowed by the black hole. For large charge this hair has dramatic effect on black hole dynamics. Our findings can have interesting astrophysical consequences, such as existence of black holes with large detectable baryonic and leptonic numbers.
Acceleration of black hole universe
Zhang, T. X.; Frederick, C.
2014-01-01
Recently, Zhang slightly modified the standard big bang theory and developed a new cosmological model called black hole universe, which is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain all observations of the universe. Previous studies accounted for the origin, structure, evolution, expansion, and cosmic microwave background radiation of the black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This paper investigates acceleration of the black hole universe and provides an alternative explanation for the redshift and luminosity distance measurements of type Ia supernovae. The results indicate that the black hole universe accelerates its expansion when it accretes the ambient matter in an increasing rate. In other words, i.e., when the second-order derivative of the mass of the black hole universe with respect to the time is positive . For a constant deceleration parameter , we can perfectly explain the type Ia supernova measurements with the reduced chi-square to be very close to unity, χ red˜1.0012. The expansion and acceleration of black hole universe are driven by external energy.
On black hole horizon fluctuations
International Nuclear Information System (INIS)
Tuchin, K.L.
1999-01-01
A study of the high angular momentum particles 'atmosphere' near the Schwarzschild black hole horizon suggested that strong gravitational interactions occur at invariant distance of the order of 3 √M [2]. We present a generalization of this result to the Kerr-Newman black hole case. It is shown that the larger charge and angular momentum black hole bears, the larger invariant distance at which strong gravitational interactions occur becomes. This invariant distance is of order 3 √((r + 2 )/((r + - r - ))). This implies that the Planckian structure of the Hawking radiation of extreme black holes is completely broken
Black holes and the multiverse
International Nuclear Information System (INIS)
Garriga, Jaume; Vilenkin, Alexander; Zhang, Jun
2016-01-01
Vacuum bubbles may nucleate and expand during the inflationary epoch in the early universe. After inflation ends, the bubbles quickly dissipate their kinetic energy; they come to rest with respect to the Hubble flow and eventually form black holes. The fate of the bubble itself depends on the resulting black hole mass. If the mass is smaller than a certain critical value, the bubble collapses to a singularity. Otherwise, the bubble interior inflates, forming a baby universe, which is connected to the exterior FRW region by a wormhole. A similar black hole formation mechanism operates for spherical domain walls nucleating during inflation. As an illustrative example, we studied the black hole mass spectrum in the domain wall scenario, assuming that domain walls interact with matter only gravitationally. Our results indicate that, depending on the model parameters, black holes produced in this scenario can have significant astrophysical effects and can even serve as dark matter or as seeds for supermassive black holes. The mechanism of black hole formation described in this paper is very generic and has important implications for the global structure of the universe. Baby universes inside super-critical black holes inflate eternally and nucleate bubbles of all vacua allowed by the underlying particle physics. The resulting multiverse has a very non-trivial spacetime structure, with a multitude of eternally inflating regions connected by wormholes. If a black hole population with the predicted mass spectrum is discovered, it could be regarded as evidence for inflation and for the existence of a multiverse
Black holes and the multiverse
Energy Technology Data Exchange (ETDEWEB)
Garriga, Jaume [Departament de Fisica Fonamental i Institut de Ciencies del Cosmos, Universitat de Barcelona, Marti i Franques, 1, Barcelona, 08028 Spain (Spain); Vilenkin, Alexander; Zhang, Jun, E-mail: jaume.garriga@ub.edu, E-mail: vilenkin@cosmos.phy.tufts.edu, E-mail: jun.zhang@tufts.edu [Institute of Cosmology, Tufts University, 574 Boston Ave, Medford, MA, 02155 (United States)
2016-02-01
Vacuum bubbles may nucleate and expand during the inflationary epoch in the early universe. After inflation ends, the bubbles quickly dissipate their kinetic energy; they come to rest with respect to the Hubble flow and eventually form black holes. The fate of the bubble itself depends on the resulting black hole mass. If the mass is smaller than a certain critical value, the bubble collapses to a singularity. Otherwise, the bubble interior inflates, forming a baby universe, which is connected to the exterior FRW region by a wormhole. A similar black hole formation mechanism operates for spherical domain walls nucleating during inflation. As an illustrative example, we studied the black hole mass spectrum in the domain wall scenario, assuming that domain walls interact with matter only gravitationally. Our results indicate that, depending on the model parameters, black holes produced in this scenario can have significant astrophysical effects and can even serve as dark matter or as seeds for supermassive black holes. The mechanism of black hole formation described in this paper is very generic and has important implications for the global structure of the universe. Baby universes inside super-critical black holes inflate eternally and nucleate bubbles of all vacua allowed by the underlying particle physics. The resulting multiverse has a very non-trivial spacetime structure, with a multitude of eternally inflating regions connected by wormholes. If a black hole population with the predicted mass spectrum is discovered, it could be regarded as evidence for inflation and for the existence of a multiverse.
International Nuclear Information System (INIS)
1988-12-01
In 1984, the Black Report published its results on the incidence of cancer and leukaemia in under 25-year olds in the village of Seascale and the surrounding area near the Sellafield nuclear reprocessing plant. Since then the pressure group core, as a result of their own independent research, has discovered ten additional cases of childhood cancer which should have been included in the Black Report and a Further two cases since the Black Report was written. This represents an additional 31% over the initial numbers considered and a review of the Black Report is sought. (UK)
Statistical Hair on Black Holes
International Nuclear Information System (INIS)
Strominger, A.
1996-01-01
The Bekenstein-Hawking entropy for certain BPS-saturated black holes in string theory has recently been derived by counting internal black hole microstates at weak coupling. We argue that the black hole microstate can be measured by interference experiments even in the strong coupling region where there is clearly an event horizon. Extracting information which is naively behind the event horizon is possible due to the existence of statistical quantum hair carried by the black hole. This quantum hair arises from the arbitrarily large number of discrete gauge symmetries present in string theory. copyright 1996 The American Physical Society
Thermodynamics of Accelerating Black Holes.
Appels, Michael; Gregory, Ruth; Kubizňák, David
2016-09-23
We address a long-standing problem of describing the thermodynamics of an accelerating black hole. We derive a standard first law of black hole thermodynamics, with the usual identification of entropy proportional to the area of the event horizon-even though the event horizon contains a conical singularity. This result not only extends the applicability of black hole thermodynamics to realms previously not anticipated, it also opens a possibility for studying novel properties of an important class of exact radiative solutions of Einstein equations describing accelerated objects. We discuss the thermodynamic volume, stability, and phase structure of these black holes.
International Nuclear Information System (INIS)
Schoute-Vanneck, H.; Scourfield, M.W.J.; Nielsen, E.
1990-01-01
Characteristics of eastward drifting forms, previously described in the literature as black aurorae, have been identified in low-light level TV camera data. The TV field of view was within the field of view of STARE and that of an all-sky camera. On the basis of these observations the authors propose that these auroral forms are a manifestation of folds or waves on the borders of auroral bands propagating along the dark regions between neighboring auroral bands. Conditions under which the folds or waves occur are compatible with their formation by the Kelvin-Helmholtz electrostatic instability
Energy Technology Data Exchange (ETDEWEB)
Ramani, R.V.; Frantz, R.L. [Pennsylvania State University, University Park, PA (United States)
1995-12-31
Coal workers` pneumoconiosis (CWP), often called Black Lung Disease is a occupational disease which results from inhalation of coal mine dust which usually contains small amounts of free crystalline silica. This chapter reviews the current knowledge of the epidemiology and clinical aspects of CWP and how it has been controlled in the USA through the 1969 Coal Mine Act and dust level standards. It describes the sampling methods used. Medical control methods and engineering control of the disease is discussed. Work of the Generic Mineral Technology Center for Respirable Dust is described. 28 refs., 6 figs.
Visser, Matt; Volovik, Grigory E
2009-01-01
Physicists are pondering on the possibility of simulating black holes in the laboratory by means of various "analog models". These analog models, typically based on condensed matter physics, can be used to help us understand general relativity (Einstein's gravity); conversely, abstract techniques developed in general relativity can sometimes be used to help us understand certain aspects of condensed matter physics. This book contains 13 chapters - written by experts in general relativity, particle physics, and condensed matter physics - that explore various aspects of this two-way traffic.
Directory of Open Access Journals (Sweden)
Roberto Casadio
2015-10-01
Full Text Available We review some features of Bose–Einstein condensate (BEC models of black holes obtained by means of the horizon wave function formalism. We consider the Klein–Gordon equation for a toy graviton field coupled to a static matter current in a spherically-symmetric setup. The classical field reproduces the Newtonian potential generated by the matter source, while the corresponding quantum state is given by a coherent superposition of scalar modes with a continuous occupation number. An attractive self-interaction is needed for bound states to form, the case in which one finds that (approximately one mode is allowed, and the system of N bosons can be self-confined in a volume of the size of the Schwarzschild radius. The horizon wave function formalism is then used to show that the radius of such a system corresponds to a proper horizon. The uncertainty in the size of the horizon is related to the typical energy of Hawking modes: it decreases with the increasing of the black hole mass (larger number of gravitons, resulting in agreement with the semiclassical calculations and which does not hold for a single very massive particle. The spectrum of these systems has two components: a discrete ground state of energy m (the bosons forming the black hole and a continuous spectrum with energy ω > m (representing the Hawking radiation and modeled with a Planckian distribution at the expected Hawking temperature. Assuming the main effect of the internal scatterings is the Hawking radiation, the N-particle state can be collectively described by a single-particle wave-function given by a superposition of a total ground state with energy M = Nm and Entropy 2015, 17 6894 a Planckian distribution for E > M at the same Hawking temperature. This can be used to compute the partition function and to find the usual area law for the entropy, with a logarithmic correction related to the Hawking component. The backreaction of modes with ω > m is also shown to reduce
Roldán-Molina, A; Nunez, Alvaro S; Duine, R A
2017-02-10
We show that the interaction between the spin-polarized current and the magnetization dynamics can be used to implement black-hole and white-hole horizons for magnons-the quanta of oscillations in the magnetization direction in magnets. We consider three different systems: easy-plane ferromagnetic metals, isotropic antiferromagnetic metals, and easy-plane magnetic insulators. Based on available experimental data, we estimate that the Hawking temperature can be as large as 1 K. We comment on the implications of magnonic horizons for spin-wave scattering and transport experiments, and for magnon entanglement.
Black American and Nigerian Pentecostalism: A Black Religious ...
African Journals Online (AJOL)
Black American and Nigerian Pentecostalism: A Black Religious Schizophrenia, 1910-2010. ... in American and African Pentecostalism as is related to social crisis, the dislocation of masses brought on by economic deprivation, urbanization, the break up of traditional society and consequence loss of traditional values.
The Effect of Black Peers on Black Test Scores
Armor, David J.; Duck, Stephanie
2007-01-01
Recent studies have used increasingly complex methodologies to estimate the effect of peer characteristics--race, poverty, and ability--on student achievement. A paper by Hanushek, Kain, and Rivkin using Texas state testing data has received particularly wide attention because it found a large negative effect of school percent black on black math…
Black Interpretation, Black American Literature, and Grey Audiences.
Washington, Earl M.
1981-01-01
Defines and illustrates language techniques used by Black authors writing to and for Blacks in the 1960s and 1970s. Suggests how language and theme barriers of such literature might be overcome in a contemporary integrated oral interpretation classroom. (PD)
Black hole thermodynamical entropy
International Nuclear Information System (INIS)
Tsallis, Constantino; Cirto, Leonardo J.L.
2013-01-01
As early as 1902, Gibbs pointed out that systems whose partition function diverges, e.g. gravitation, lie outside the validity of the Boltzmann-Gibbs (BG) theory. Consistently, since the pioneering Bekenstein-Hawking results, physically meaningful evidence (e.g., the holographic principle) has accumulated that the BG entropy S BG of a (3+1) black hole is proportional to its area L 2 (L being a characteristic linear length), and not to its volume L 3 . Similarly it exists the area law, so named because, for a wide class of strongly quantum-entangled d-dimensional systems, S BG is proportional to lnL if d=1, and to L d-1 if d>1, instead of being proportional to L d (d ≥ 1). These results violate the extensivity of the thermodynamical entropy of a d-dimensional system. This thermodynamical inconsistency disappears if we realize that the thermodynamical entropy of such nonstandard systems is not to be identified with the BG additive entropy but with appropriately generalized nonadditive entropies. Indeed, the celebrated usefulness of the BG entropy is founded on hypothesis such as relatively weak probabilistic correlations (and their connections to ergodicity, which by no means can be assumed as a general rule of nature). Here we introduce a generalized entropy which, for the Schwarzschild black hole and the area law, can solve the thermodynamic puzzle. (orig.)
International Nuclear Information System (INIS)
Mathur, Samir D
2012-01-01
The idea of holography in gravity arose from the fact that the entropy of black holes is given by their surface area. The holography encountered in gauge/gravity duality has no such relation however; the boundary surface can be placed at an arbitrary location in AdS space and its area does not give the entropy of the bulk. The essential issues are also different between the two cases: in black holes we get Hawking radiation from the 'holographic surface' which leads to the information issue, while in gauge/gravity duality there is no such radiation. To resolve the information paradox we need to show that there are real degrees of freedom at the horizon of the hole; this is achieved by the fuzzball construction. In gauge/gravity duality we have instead a field theory defined on an abstract dual space; there are no gravitational degrees of freedom at the holographic boundary. It is important to understand the relations and differences between these two notions of holography to get a full understanding of the lessons from the information paradox.
Statistical black-hole thermodynamics
International Nuclear Information System (INIS)
Bekenstein, J.D.
1975-01-01
Traditional methods from statistical thermodynamics, with appropriate modifications, are used to study several problems in black-hole thermodynamics. Jaynes's maximum-uncertainty method for computing probabilities is used to show that the earlier-formulated generalized second law is respected in statistically averaged form in the process of spontaneous radiation by a Kerr black hole discovered by Hawking, and also in the case of a Schwarzschild hole immersed in a bath of black-body radiation, however cold. The generalized second law is used to motivate a maximum-entropy principle for determining the equilibrium probability distribution for a system containing a black hole. As an application we derive the distribution for the radiation in equilibrium with a Kerr hole (it is found to agree with what would be expected from Hawking's results) and the form of the associated distribution among Kerr black-hole solution states of definite mass. The same results are shown to follow from a statistical interpretation of the concept of black-hole entropy as the natural logarithm of the number of possible interior configurations that are compatible with the given exterior black-hole state. We also formulate a Jaynes-type maximum-uncertainty principle for black holes, and apply it to obtain the probability distribution among Kerr solution states for an isolated radiating Kerr hole
Introduction: Teaching Black Lives Matter
Paula Austin; Erica Cardwell; Christopher Kennedy; Robyn Spencer
2016-01-01
An introduction to Radical Teacher, Issue 106: Teaching Black Lives Matter. This issue brings together a diverse collection of articles exploring educator’s responses, strategies, and stories on how #BlackLivesMatter has informed their teaching practice, the content of their courses, and their personal relationship to colleagues, family, friends, and self.
Introduction: Teaching Black Lives Matter
Directory of Open Access Journals (Sweden)
Paula Austin
2016-11-01
Full Text Available An introduction to Radical Teacher, Issue 106: Teaching Black Lives Matter. This issue brings together a diverse collection of articles exploring educator’s responses, strategies, and stories on how #BlackLivesMatter has informed their teaching practice, the content of their courses, and their personal relationship to colleagues, family, friends, and self.
Teaching Black History after Obama
Sotiropoulos, Karen
2017-01-01
This article is a reflection on the teaching of black history after the Obama presidency and at the dawn of the Trump era. It is both an analysis of the state of the academic field and a primer on how to integrate the past few decades of scholarship in black history broadly across standard K-12 curriculum. It demonstrates the importance of…
DEFF Research Database (Denmark)
Vestergaard, Marianne
2004-01-01
The applicability and apparent uncertainties of the techniques currently available for measuring or estimating black-hole masses in AGNs are briefly summarized.......The applicability and apparent uncertainties of the techniques currently available for measuring or estimating black-hole masses in AGNs are briefly summarized....
School Desegregation and Black Achievement.
Cook, Thomas; And Others
Seven papers commissioned by the National Institute of Education in order to clarify the state of recent knowledge about the effects of school desegregation on the academic achievement of black students are contained in this report. The papers, which analyze 19 "core" empirical studies on this topic, include: (1) "What Have Black Children Gained…
ATLAS simulated black hole event
Pequenão, J
2008-01-01
The simulated collision event shown is viewed along the beampipe. The event is one in which a microscopic-black-hole was produced in the collision of two protons (not shown). The microscopic-black-hole decayed immediately into many particles. The colors of the tracks show different types of particles emerging from the collision (at the center).
Indian Academy of Sciences (India)
Abstract. A Kerr metric describing a rotating black hole is obtained on the three brane in a five-dimensional Randall-Sundrum brane world by considering a rotating five-dimensional black string in the bulk. We examine the causal structure of this space-time through the geodesic equations.
Black holes and quantum processes in them
International Nuclear Information System (INIS)
Frolov, V.P.
1976-01-01
The latest achievements in the physics of black holes are reviewed. The problem of quantum production in a strong gravitational field of black holes is considered. Another parallel discovered during investigation of interactions between black holes and between black holes and surrounding media, is also drawn with thermodynamics. A gravitational field of rotating black holes is considered. Some cosmological aspects of evaporation of small black holes are discussed as well as possibilities to observe them
Black hole decay as geodesic motion
International Nuclear Information System (INIS)
Gupta, Kumar S.; Sen, Siddhartha
2003-01-01
We show that a formalism for analyzing the near-horizon conformal symmetry of Schwarzschild black holes using a scalar field probe is capable of describing black hole decay. The equation governing black hole decay can be identified as the geodesic equation in the space of black hole masses. This provides a novel geometric interpretation for the decay of black holes. Moreover, this approach predicts a precise correction term to the usual expression for the decay rate of black holes
Black holes and everyday physics
International Nuclear Information System (INIS)
Bekenstein, J.D.
1982-01-01
Black holes have piqued much curiosity. But thus far they have been important only in ''remote'' subjects like astrophysics and quantum gravity. It is shown that the situation can be improved. By a judicious application of black hole physics, one can obtain new results in ''everyday physics''. For example, black holes yield a quantum universal upper bound on the entropy-to-energy ratio for ordinary thermodynamical systems which was unknown earlier. It can be checked, albeit with much labor, by ordinary statistical methods. Black holes set a limitation on the number of species of elementary particles-quarks, leptons, neutrinos - which may exist. And black holes lead to a fundamental limitation on the rate at which information can be transferred for given message energy by any communication system. (author)
International Nuclear Information System (INIS)
Torn, K.
1976-01-01
Conceivable experimental investigations to prove the existence of black holes are discussed. Double system with a black hole turning around a star-satellite are in the spotlight. X-radiation emmited by such systems and resulting from accretion of the stellar gas by a black hole, and the gas heating when falling on the black hole might prove the model suggested. A source of strong X-radiation observed in the Cygnus star cluster and referred to as Cygnus X-1 may be thus identified as a black hole. Direct registration of short X-ray pulses with msec intervals might prove the suggestion. The lack of appropriate astrophysic facilities is pointed out to be the major difficulty on the way of experimental verifications
Black hole final state conspiracies
International Nuclear Information System (INIS)
McInnes, Brett
2009-01-01
The principle that unitarity must be preserved in all processes, no matter how exotic, has led to deep insights into boundary conditions in cosmology and black hole theory. In the case of black hole evaporation, Horowitz and Maldacena were led to propose that unitarity preservation can be understood in terms of a restriction imposed on the wave function at the singularity. Gottesman and Preskill showed that this natural idea only works if one postulates the presence of 'conspiracies' between systems just inside the event horizon and states at much later times, near the singularity. We argue that some AdS black holes have unusual internal thermodynamics, and that this may permit the required 'conspiracies' if real black holes are described by some kind of sum over all AdS black holes having the same entropy
Compressibility of rotating black holes
International Nuclear Information System (INIS)
Dolan, Brian P.
2011-01-01
Interpreting the cosmological constant as a pressure, whose thermodynamically conjugate variable is a volume, modifies the first law of black hole thermodynamics. Properties of the resulting thermodynamic volume are investigated: the compressibility and the speed of sound of the black hole are derived in the case of nonpositive cosmological constant. The adiabatic compressibility vanishes for a nonrotating black hole and is maximal in the extremal case--comparable with, but still less than, that of a cold neutron star. A speed of sound v s is associated with the adiabatic compressibility, which is equal to c for a nonrotating black hole and decreases as the angular momentum is increased. An extremal black hole has v s 2 =0.9 c 2 when the cosmological constant vanishes, and more generally v s is bounded below by c/√(2).
When Supermassive Black Holes Wander
Kohler, Susanna
2018-05-01
Are supermassive black holes found only at the centers of galaxies? Definitely not, according to a new study in fact, galaxies like the Milky Way may harbor several such monsters wandering through their midst.Collecting Black Holes Through MergersIts generally believed that galaxies are built up hierarchically, growing in size through repeated mergers over time. Each galaxy in a major merger likely hosts a supermassive black hole a black hole of millions to billions of times the mass of the Sun at its center. When a pair of galaxies merges, their supermassive black holes will often sink to the center of the merger via a process known as dynamical friction. There the supermassive black holes themselves will eventually merge in a burst of gravitational waves.Spatial distribution and velocities of wandering supermassive black holes in three of the authors simulated galaxies, shown in edge-on (left) and face-on (right) views of the galaxy disks. Click for a closer look. [Tremmel et al. 2018]But if a galaxy the size of the Milky Way was built through a history of many major galactic mergers, are we sure that all its accumulated supermassive black holes eventually merged at the galactic center? A new study suggests that some of these giants might have escaped such a fate and they now wander unseen on wide orbits through their galaxies.Black Holes in an Evolving UniverseLed by Michael Tremmel (Yale Center for Astronomy Astrophysics), a team of scientists has used data from a large-scale cosmological simulation, Romulus25, to explore the possibility of wandering supermassive black holes. The Romulus simulations are uniquely suited to track the formation and subsequent orbital motion of supermassive black holes as galactic halos are built up through mergers over the history of the universe.From these simulations, Tremmel and collaborators find an end total of 316 supermassive black holes residing within the bounds of 26 Milky-Way-mass halos. Of these, roughly a third are
Nyachae, Tiffany M.
2016-01-01
Millennial Black women teachers wrestle with two simultaneous burdens: disrupting the racist and sexist status quo of schooling through curriculum, and employing tactics to survive school politics among their majority White women colleagues. This article describes how the "Sisters of Promise" (SOP) curriculum aligned with Black feminism…
Mutsaers, Paul
2017-01-01
The question 'who is the victim?' is an important social directive that shapes the struggles for victimhood in which Black Lives Matters, U.S. police forces and their various (counter)publics are currently engaging. This column begins with a controversial FBI report on so-called Black Identity
A nonsingular rotating black hole
International Nuclear Information System (INIS)
Ghosh, Sushant G.
2015-01-01
The spacetime singularities in classical general relativity are inevitable, as predicated by the celebrated singularity theorems. However, it is a general belief that singularities do not exist in Nature and that they are the limitations of the general relativity. In the absence of a welldefined quantum gravity, models of regular black holes have been studied. We employ a probability distribution inspired mass function m(r) to replace the Kerr black hole mass M to represent a nonsingular rotating black hole that is identified asymptotically (r >> k, k > 0 constant) exactly as the Kerr-Newman black hole, and as the Kerr black hole when k = 0. The radiating counterpart renders a nonsingular generalization of Carmeli's spacetime as well as Vaidya's spacetime, in the appropriate limits. The exponential correction factor changing the geometry of the classical black hole to remove the curvature singularity can also be motivated by quantum arguments. The regular rotating spacetime can also be understood as a black hole of general relativity coupled to nonlinear electrodynamics. (orig.)
The renaissance of black phosphorus.
Ling, Xi; Wang, Han; Huang, Shengxi; Xia, Fengnian; Dresselhaus, Mildred S
2015-04-14
One hundred years after its first successful synthesis in the bulk form in 1914, black phosphorus (black P) was recently rediscovered from the perspective of a 2D layered material, attracting tremendous interest from condensed matter physicists, chemists, semiconductor device engineers, and material scientists. Similar to graphite and transition metal dichalcogenides (TMDs), black P has a layered structure but with a unique puckered single-layer geometry. Because the direct electronic band gap of thin film black P can be varied from 0.3 eV to around 2 eV, depending on its film thickness, and because of its high carrier mobility and anisotropic in-plane properties, black P is promising for novel applications in nanoelectronics and nanophotonics different from graphene and TMDs. Black P as a nanomaterial has already attracted much attention from researchers within the past year. Here, we offer our opinions on this emerging material with the goal of motivating and inspiring fellow researchers in the 2D materials community and the broad readership of PNAS to discuss and contribute to this exciting new field. We also give our perspectives on future 2D and thin film black P research directions, aiming to assist researchers coming from a variety of disciplines who are desirous of working in this exciting research field.
2006-01-01
[figure removed for brevity, see original site] Poster Version This artist's concept shows a supermassive black hole at the center of a remote galaxy digesting the remnants of a star. NASA's Galaxy Evolution Explorer had a 'ringside' seat for this feeding frenzy, using its ultraviolet eyes to study the process from beginning to end. The artist's concept chronicles the star being ripped apart and swallowed by the cosmic beast over time. First, the intact sun-like star (left) ventures too close to the black hole, and its own self-gravity is overwhelmed by the black hole's gravity. The star then stretches apart (middle yellow blob) and eventually breaks into stellar crumbs, some of which swirl into the black hole (cloudy ring at right). This doomed material heats up and radiates light, including ultraviolet light, before disappearing forever into the black hole. The Galaxy Evolution Explorer was able to watch this process unfold by observing changes in ultraviolet light. The area around the black hole appears warped because the gravity of the black hole acts like a lens, twisting and distorting light.
Black holes at neutrino telescopes
International Nuclear Information System (INIS)
Kowalski, M.; Ringwald, A.; Tu, H.
2002-01-01
In scenarios with extra dimensions and TeV-scale quantum gravity, black holes are expected to be produced in the collision of light particles at center-of-mass energies above the fundamental Planck scale with small impact parameters. Black hole production and evaporation may thus be studied in detail at the large hadron collider (LHC). But even before the LHC starts operating, neutrino telescopes such as AMANDA/IceCube, ANTARES, Baikal, and RICE have an opportunity to search for black hole signatures. Black hole production in the scattering of ultrahigh energy cosmic neutrinos on nucleons in the ice or water may initiate cascades and through-going muons with distinct characteristics above the Standard Model rate. In this Letter, we investigate the sensitivity of neutrino telescopes to black hole production and compare it to the one expected at the Pierre Auger Observatory, an air shower array currently under construction, and at the LHC. We find that, already with the currently available data, AMANDA and RICE should be able to place sensible constraints in black hole production parameter space, which are competitive with the present ones from the air shower facilities Fly's Eye and AGASA. In the optimistic case that a ultrahigh energy cosmic neutrino flux significantly higher than the one expected from cosmic ray interactions with the cosmic microwave background radiation is realized in nature, one even has discovery potential for black holes at neutrino telescopes beyond the reach of LHC. (orig.)
International Nuclear Information System (INIS)
Punsly, B.M.
1988-01-01
This dissertation is a study of the physical mechanism that allows a large scale magnetic field to torque a rapidly rotating, supermassive black hole. This is an interesting problem as it has been conjectured that rapidly rotating black holes are the central engines that power the observed extragalactic double radio sources. Axisymmetric solutions of the curved space-time version of Maxwell's equations in the vacuum do not torque black holes. Plasma must be introduced for the hole to mechanically couple to the field. The dynamical aspect of rotating black holes that couples the magnetic field to the hole is the following. A rotating black hole forces the external geometry of space-time to rotate (the dragging of inertial frames). Inside of the stationary limit surface, the ergosphere, all physical particle trajectories must appear to rotate in the same direction as the black hole as viewed by the stationary observers at asymptotic infinity. In the text, it is demonstrated how plasma that is created on field lines that thread both the ergosphere and the equatorial plane will be pulled by gravity toward the equator. By the aforementioned properties of the ergosphere, the disk must rotate. Consequently, the disk acts like a unipolar generator. It drives a global current system that supports the toroidal magnetic field in an outgoing, magnetically dominated wind. This wind carries energy (mainly in the form of Poynting flux) and angular momentum towards infinity. The spin down of the black hole is the ultimate source of this energy and angular momentum flux
Energy Technology Data Exchange (ETDEWEB)
Sherik, Abdelmounam [Saudi Aramco, Dhahran (Saudi Arabia)
2009-07-01
Despite its common occurrence in the gas industry, black powder is a problem that is not well understood across the industry, in terms of its chemical and physical properties, source, formation, prevention or management of its impacts. In order to prevent or effectively manage the impacts of black powder, it is essential to have knowledge of its chemical and physical properties, formation mechanisms and sources. The present paper is divided into three parts. The first part of this paper is a synopsis of published literature. The second part reviews the recent laboratory and field work conducted at Saudi Aramco Research and Development Center to determine the compositions, properties, sources and formation mechanisms of black powder in gas transmission systems. Microhardness, nano-indentation, X-ray Diffraction (XRD), X-ray Fluorescence (XRF) and Scanning Electron Microscopy (SEM) techniques were used to analyze a large number of black powder samples collected from the field. Our findings showed that black powder is generated inside pipelines due to internal corrosion and that the composition of black powder is dependent on the composition of transported gas. The final part presents a summary and brief discussion of various black powder management methods. (author)
Thermodynamic theory of black holes
Energy Technology Data Exchange (ETDEWEB)
Davies, P C.W. [King' s Coll., London (UK). Dept. of Mathematics
1977-04-21
The thermodynamic theory underlying black hole processes is developed in detail and applied to model systems. It is found that Kerr-Newman black holes undergo a phase transition at a = 0.68M or Q = 0.86M, where the heat capacity has an infinite discontinuity. Above the transition values the specific heat is positive, permitting isothermal equilibrium with a surrounding heat bath. Simple processes and stability criteria for various black hole situations are investigated. The limits for entropically favoured black hole formation are found. The Nernst conditions for the third law of thermodynamics are not satisfied fully for black holes. There is no obvious thermodynamic reason why a black hole may not be cooled down below absolute zero and converted into a naked singularity. Quantum energy-momentum tensor calculations for uncharged black holes are extended to the Reissner-Nordstrom case, and found to be fully consistent with the thermodynamic picture for Q < M. For Q < M the model predicts that 'naked' collapse also produces radiation, with such intensity that the collapsing matter is entirely evaporated away before a naked singularity can form.
Directory of Open Access Journals (Sweden)
D. I. Pikulin
2017-07-01
Full Text Available A system of Majorana zero modes with random infinite-range interactions—the Sachdev-Ye-Kitaev (SYK model—is thought to exhibit an intriguing relation to the horizons of extremal black holes in two-dimensional anti–de Sitter space. This connection provides a rare example of holographic duality between a solvable quantum-mechanical model and dilaton gravity. Here, we propose a physical realization of the SYK model in a solid-state system. The proposed setup employs the Fu-Kane superconductor realized at the interface between a three-dimensional topological insulator and an ordinary superconductor. The requisite N Majorana zero modes are bound to a nanoscale hole fabricated in the superconductor that is threaded by N quanta of magnetic flux. We show that when the system is tuned to the surface neutrality point (i.e., chemical potential coincident with the Dirac point of the topological insulator surface state and the hole has sufficiently irregular shape, the Majorana zero modes are described by the SYK Hamiltonian. We perform extensive numerical simulations to demonstrate that the system indeed exhibits physical properties expected of the SYK model, including thermodynamic quantities and two-point as well as four-point correlators, and discuss ways in which these can be observed experimentally.
Black holes and Higgs stability
Tetradis, Nikolaos
2016-09-20
We study the effect of primordial black holes on the classical rate of nucleation of AdS regions within the standard electroweak vacuum. We find that the energy barrier for transitions to the new vacuum, which characterizes the exponential suppression of the nucleation rate, can be reduced significantly in the black-hole background. A precise analysis is required in order to determine whether the the existence of primordial black holes is compatible with the form of the Higgs potential at high temperature or density in the Standard Model or its extensions.
Vacuum metastability with black holes
Energy Technology Data Exchange (ETDEWEB)
Burda, Philipp [Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Gregory, Ruth [Centre for Particle Theory, Durham University,South Road, Durham, DH1 3LE (United Kingdom); Perimeter Institute, 31 Caroline Street North,Waterloo, ON, N2L 2Y5 (Canada); Moss, Ian G. annd [School of Mathematics and Statistics, Newcastle University,Newcastle Upon Tyne, NE1 7RU (United Kingdom)
2015-08-24
We consider the possibility that small black holes can act as nucleation seeds for the decay of a metastable vacuum, focussing particularly on the Higgs potential. Using a thin-wall bubble approximation for the nucleation process, which is possible when generic quantum gravity corrections are added to the Higgs potential, we show that primordial black holes can stimulate vacuum decay. We demonstrate that for suitable parameter ranges, the vacuum decay process dominates over the Hawking evaporation process. Finally, we comment on the application of these results to vacuum decay seeded by black holes produced in particle collisions.
Orbital resonances around black holes.
Brink, Jeandrew; Geyer, Marisa; Hinderer, Tanja
2015-02-27
We compute the length and time scales associated with resonant orbits around Kerr black holes for all orbital and spin parameters. Resonance-induced effects are potentially observable when the Event Horizon Telescope resolves the inner structure of Sgr A*, when space-based gravitational wave detectors record phase shifts in the waveform during the resonant passage of a compact object spiraling into the black hole, or in the frequencies of quasiperiodic oscillations for accreting black holes. The onset of geodesic chaos for non-Kerr spacetimes should occur at the resonance locations quantified here.
Vacuum metastability with black holes
International Nuclear Information System (INIS)
Burda, Philipp; Gregory, Ruth; Moss, Ian G. annd
2015-01-01
We consider the possibility that small black holes can act as nucleation seeds for the decay of a metastable vacuum, focussing particularly on the Higgs potential. Using a thin-wall bubble approximation for the nucleation process, which is possible when generic quantum gravity corrections are added to the Higgs potential, we show that primordial black holes can stimulate vacuum decay. We demonstrate that for suitable parameter ranges, the vacuum decay process dominates over the Hawking evaporation process. Finally, we comment on the application of these results to vacuum decay seeded by black holes produced in particle collisions.
Tunnelling from Goedel black holes
International Nuclear Information System (INIS)
Kerner, Ryan; Mann, R. B.
2007-01-01
We consider the spacetime structure of Kerr-Goedel black holes, analyzing their parameter space in detail. We apply the tunnelling method to compute their temperature and compare the results to previous calculations obtained via other methods. We claim that it is not possible to have the closed timelike curve (CTC) horizon in between the two black hole horizons and include a discussion of issues that occur when the radius of the CTC horizon is smaller than the radius of both black hole horizons
Quantum mechanics of black holes.
Witten, Edward
2012-08-03
The popular conception of black holes reflects the behavior of the massive black holes found by astronomers and described by classical general relativity. These objects swallow up whatever comes near and emit nothing. Physicists who have tried to understand the behavior of black holes from a quantum mechanical point of view, however, have arrived at quite a different picture. The difference is analogous to the difference between thermodynamics and statistical mechanics. The thermodynamic description is a good approximation for a macroscopic system, but statistical mechanics describes what one will see if one looks more closely.
Gravitational polarizability of black holes
International Nuclear Information System (INIS)
Damour, Thibault; Lecian, Orchidea Maria
2009-01-01
The gravitational polarizability properties of black holes are compared and contrasted with their electromagnetic polarizability properties. The 'shape' or 'height' multipolar Love numbers h l of a black hole are defined and computed. They are then compared to their electromagnetic analogs h l EM . The Love numbers h l give the height of the lth multipolar 'tidal bulge' raised on the horizon of a black hole by faraway masses. We also discuss the shape of the tidal bulge raised by a test-mass m, in the limit where m gets very close to the horizon.
Black layers on historical architecture.
Toniolo, Lucia; Zerbi, Carlotta M; Bugini, Roberto
2009-03-01
The external surface of any building in urban polluted environment is unavoidably destined to be covered with layers that assume a grey to black colour and are generally called 'black crusts'. These, according to standard protocols and glossary, are deteriorated surface layers of stone material; they can have variable thickness, are hard and fragile and can detach spontaneously from the substrate, which, in general, is quite decayed. Plain visual examination may lead to consider 'black crusts' all similar, whilst only a careful diagnostic investigation can distinguish 'black crusts' and the consequences of their formation on stone substrates. In this paper, various black layers on marble are studied and compared and the morphological and compositional characteristics discussed according to the related mechanisms of formation. Differences between old (hundred years) and recent crusts (30 years) are investigated and pointed out. Samples of black crusts collected from the Milan Cathedral façade (Candoglia Marble) have been studied and compared with the careful and synergic employ of traditional techniques: optical (transmission and reflected VIS light) and electron microscopy, X-ray spectrometry and micro-Fourier transform infrared spectroscopy. Visual examination of loose fragments does not allow to point out outstanding differences amongst the various samples; black layers have similar main mineral components, gypsum and airborne particles, with different spatial distribution. The microscopic studies allowed to point out the porosity differences, the gypsum crystallisation habit, different amount of embedded particles, level and progress of marble decay. The observations lead to define three main types of black crusts: black crust deriving from marble sulphation, compact deposit and encrustation due to exogenic materials deposition. Black crusts show evidence of sulphation in progress, without a clear continuity solution between crust and marble; the lack of
Erratic Black Hole Regulates Itself
2009-03-01
New results from NASA's Chandra X-ray Observatory have made a major advance in explaining how a special class of black holes may shut off the high-speed jets they produce. These results suggest that these black holes have a mechanism for regulating the rate at which they grow. Black holes come in many sizes: the supermassive ones, including those in quasars, which weigh in at millions to billions of times the mass of the Sun, and the much smaller stellar-mass black holes which have measured masses in the range of about 7 to 25 times the Sun's mass. Some stellar-mass black holes launch powerful jets of particles and radiation, like seen in quasars, and are called "micro-quasars". The new study looks at a famous micro-quasar in our own Galaxy, and regions close to its event horizon, or point of no return. This system, GRS 1915+105 (GRS 1915 for short), contains a black hole about 14 times the mass of the Sun that is feeding off material from a nearby companion star. As the material swirls toward the black hole, an accretion disk forms. This system shows remarkably unpredictable and complicated variability ranging from timescales of seconds to months, including 14 different patterns of variation. These variations are caused by a poorly understood connection between the disk and the radio jet seen in GRS 1915. Chandra, with its spectrograph, has observed GRS 1915 eleven times since its launch in 1999. These studies reveal that the jet in GRS 1915 may be periodically choked off when a hot wind, seen in X-rays, is driven off the accretion disk around the black hole. The wind is believed to shut down the jet by depriving it of matter that would have otherwise fueled it. Conversely, once the wind dies down, the jet can re-emerge. "We think the jet and wind around this black hole are in a sort of tug of war," said Joseph Neilsen, Harvard graduate student and lead author of the paper appearing in the journal Nature. "Sometimes one is winning and then, for reasons we don
Black Hole Complementary Principle and Noncommutative Membrane
International Nuclear Information System (INIS)
Wei Ren
2006-01-01
In the spirit of black hole complementary principle, we have found the noncommutative membrane of Scharzchild black holes. In this paper we extend our results to Kerr black hole and see the same story. Also we make a conjecture that spacetimes are noncommutative on the stretched membrane of the more general Kerr-Newman black hole.
The Black Man in American Society.
Framingham Public Schools, MA.
GRADE OR AGES: Junior high school. SUBJECT MATTER: The black man in American society. ORGANIZATION AND PHYSICAL APPEARANCE: There are four major parts each with an overview. The four parts concern a) the African heritage of the black man, b) the American exploitation of the black man, c) the black man's contribution to American society, d) the…
The Core Journal Concept in Black Studies
Weissinger, Thomas
2010-01-01
Black Studies scholars have shown interest in the core journal concept. Indeed, the idea of core journals for the study of the Black experience has changed several times since 1940. While Black Studies scholars are citing Black Studies journals with frequency, they also cite traditional disciplinary journals a great deal of the time. However,…
Accretion, primordial black holes and standard cosmology
Indian Academy of Sciences (India)
Primordial black holes evaporate due to Hawking radiation. We find that the evaporation times of primordial black holes increase when accretion of radiation is included. Thus, depending on accretion efficiency, more primordial black holes are existing today, which strengthens the conjecture that the primordial black holes ...
The Black Journalist in South Africa.
Hachten, William A.
The role of the black journalist in South Africa is contradictory, precarious, and permeated with politics. There is little freedom of expression for blacks in South Africa, yet white-owned newspapers have expanded their coverage of black news, and some have special editions for black readers. As a result, the English language press is using more…
Black Films in Search of a Home.
Taylor, Clyde
1983-01-01
Black filmmakers have produced many films that successfully showcase African-American culture, yet this work is rarely exposed to its intended audience. The Black bourgeoisie, because of their money and social status, must play a role in supporting Black filmmaking and fostering the perception of Black film as part of American popular culture. (GC)
Then and Now: Black Boycott in Waterloo.
Anderson, Ruth B.
1983-01-01
Discusses events following the desegregation of Waterloo, Iowa, schools. Describes the 1978 Black boycott of Hoover Junior High, which led to improvements in the treatment of Black students. Lists administrative responses to each Black grievance, and presents interviews with ten Black students three years after the boycott. (KH)
Black hole evaporation: a paradigm
International Nuclear Information System (INIS)
Ashtekar, Abhay; Bojowald, Martin
2005-01-01
A paradigm describing black hole evaporation in non-perturbative quantum gravity is developed by combining two sets of detailed results: (i) resolution of the Schwarzschild singularity using quantum geometry methods and (ii) time evolution of black holes in the trapping and dynamical horizon frameworks. Quantum geometry effects introduce a major modification in the traditional spacetime diagram of black hole evaporation, providing a possible mechanism for recovery of information that is classically lost in the process of black hole formation. The paradigm is developed directly in the Lorentzian regime and necessary conditions for its viability are discussed. If these conditions are met, much of the tension between expectations based on spacetime geometry and structure of quantum theory would be resolved
Black Sprayable Molecular Adsorber Coating
National Aeronautics and Space Administration — The main objective of this technology project is to develop, optimize, and flight qualify a black version of the molecular adsorber coating and a conductive version...
Black holes by analytic continuation
Amati, Daniele
1997-01-01
In the context of a two-dimensional exactly solvable model, the dynamics of quantum black holes is obtained by analytically continuing the description of the regime where no black hole is formed. The resulting spectrum of outgoing radiation departs from the one predicted by the Hawking model in the region where the outgoing modes arise from the horizon with Planck-order frequencies. This occurs early in the evaporation process, and the resulting physical picture is unconventional. The theory predicts that black holes will only radiate out an energy of Planck mass order, stabilizing after a transitory period. The continuation from a regime without black hole formation --accessible in the 1+1 gravity theory considered-- is implicit in an S matrix approach and provides in this way a possible solution to the problem of information loss.
"Be Real Black for Me": Imagining BlackCrit in Education
Dumas, Michael J.; ross, kihana miraya
2016-01-01
The authors put forward a theorization of a Black Critical Theory, or what might be called BlackCrit, within, and in response to, Critical Race Theory, and then outline ways that BlackCrit in education helps us to more incisively analyze how the specificity of (anti)blackness matters in explaining how Black bodies become marginalized, disregarded,…
International Nuclear Information System (INIS)
Roser, T.
1993-01-01
On the 13 October the Bavarian police seized 2.2kg of uranium and arrested a group of seven people who had offered to sell it for $500.000. The existence of a black market for uranium may be a proliferation risk but it is not a serious health hazard - even if the material is negligently packed, as it seems to have been in all the recent cases. The situation is quite different when it comes to dealing with highly radioactive materials such as fission productions. Two such cases have been reported this summer involving Cs-137 and Sr-90, both emitters of hard beta rays. Little is known about the provenance of the radioactive and fissile material discovered. Obviously it originates from the ex-USSR, and the absence of highly enriched material suggests a civil rather than a military source. The governments of ex-Soviet states have apparently tried to intercept smugglers at their western frontiers, but have so far been unable to pinpoint the breaches in their security. It is also uncertain whether the occurrences discovered and reported are merely the tip of an iceberg. (author)
van Herck, Walter; Wyder, Thomas
2010-04-01
The enumeration of BPS bound states in string theory needs refinement. Studying partition functions of particles made from D-branes wrapped on algebraic Calabi-Yau 3-folds, and classifying states using split attractor flow trees, we extend the method for computing a refined BPS index, [1]. For certain D-particles, a finite number of microstates, namely polar states, exclusively realized as bound states, determine an entire partition function (elliptic genus). This underlines their crucial importance: one might call them the ‘chromosomes’ of a D-particle or a black hole. As polar states also can be affected by our refinement, previous predictions on elliptic genera are modified. This can be metaphorically interpreted as ‘crossing-over in the meiosis of a D-particle’. Our results improve on [2], provide non-trivial evidence for a strong split attractor flow tree conjecture, and thus suggest that we indeed exhaust the BPS spectrum. In the D-brane description of a bound state, the necessity for refinement results from the fact that tachyonic strings split up constituent states into ‘generic’ and ‘special’ states. These are enumerated separately by topological invariants, which turn out to be partitions of Donaldson-Thomas invariants. As modular predictions provide a check on many of our results, we have compelling evidence that our computations are correct.
New regular black hole solutions
International Nuclear Information System (INIS)
Lemos, Jose P. S.; Zanchin, Vilson T.
2011-01-01
In the present work we consider general relativity coupled to Maxwell's electromagnetism and charged matter. Under the assumption of spherical symmetry, there is a particular class of solutions that correspond to regular charged black holes whose interior region is de Sitter, the exterior region is Reissner-Nordstroem and there is a charged thin-layer in-between the two. The main physical and geometrical properties of such charged regular black holes are analyzed.
Black holes from extended inflation
International Nuclear Information System (INIS)
Hsu, S.D.H.; Lawrence Berkeley Lab., CA
1990-01-01
It is argued that models of extended inflation, in which modified Einstein gravity allows a graceful exit from the false vacuum, lead to copious production of black holes. The critical temperature of the inflationary phase transition must be >10 8 GeV in order to avoid severe cosmological problems in a universe dominated by black holes. We speculate on the possibility that the interiors of false vacuum regions evolve into baby universes. (orig.)
Linezolid induced black hairy tongue
Govindan Balaji; B Maharani; Velappan Ravichandran; Thiyagarajan Parthasarathi
2014-01-01
Black hairy tongue (BHT) also called as lingua villosa nigra, is a self limiting benign condition characterized by hypertrophy and elongation of filiform papillae of tongue with brown or black discoloration. Smoking, poor oral hygiene, xerostomia, using peroxide containing mouth washes, substance abuse and drugs (steroids, methyldopa, olanzapine, etc) are the predisposing factors. However its occurrence in relation to linezolid ingestion among south Indians has not been reported in PubMed dat...
Theorizing black (African) transnational masculinities
Pasura, Dominic; Christou, Anastasia
2017-01-01
Just as masculinity is crucial in the construction of nationhood, masculinity is also significant in the making and unmaking of transnational communities. This article focuses on how black African men negotiate and perform respectable masculinity in transnational settings, such as the workplace, community, and family. Moving away from conceptualizations of black transnational forms of masculinities as in perpetual crisis and drawing on qualitative data collected from the members of the new Af...
Black strings and classical hair
International Nuclear Information System (INIS)
Horowitz, G.T.; Yang, H.
1997-01-01
We examine the geometry near the event horizon of a family of black string solutions with traveling waves. It has previously been shown that the metric is continuous there. Contrary to expectations, we find that the geometry is not smooth, and the horizon becomes singular whenever a wave is present. Both five-dimensional and six-dimensional black strings are considered with similar results. copyright 1997 The American Physical Society
Black coal. Annual report 1997
International Nuclear Information System (INIS)
1997-01-01
An overview is given of the situation of the world energy industry with regard to all energy carriers. Then energy-political conclusions are drawn for German black coal and the resulting prospects are detailed. Finally, some socio-political aspects are considered with regard to German black-coal mining: Workforce policy, tariff policy, social security and social safeguards for the adaptation process. (orig.) [de
International Nuclear Information System (INIS)
Tipler, F.J.
1979-01-01
A definition of a black hole is proposed that should work in any stably causal space-time. This is that a black hole is the closure of the smaller future set that contains all noncosmological trapped surfaces and which has its boundary generated by null geodesic segments that are boundary generators of TIPs. This allows precise definitions of cosmic censorship and white holes. (UK)
Black holes and cosmic censorship
International Nuclear Information System (INIS)
Hiscock, W.A.
1979-01-01
It is widely accepted that the complete gravitational collapse of a body always yields a black hole, and that naked singularities are never produced (the cosmic censorship hypothesis). The local (or strong) cosmic censorship hypothesis states that singularities which are even locally naked (e.g., to an observer inside a black hole) are never produced. This dissertation studies the validity of these two conjectures. The Kerr-Newman metrics describes the black holes only when M 2 greater than or equal to Q 2 + P 2 , where M is the mass of the black hole, a = J/M its specific angular momentum, Q its electric charge, and P its magnetic charge. In the first part of this dissertation, the possibility of converting an extreme Kerr-Newman black hole (M 2 = a 2 + Q 2 + P 2 ) into a naked singularity by the accretion of test particles is considered. The motion of test particles is studied with a large angular momentum to energy ratio, and also test particles with a large charge to energy ratio. The final state is always found to be a black hole if the angular momentum, electric charge, and magnetic charge of the black hole are all much greater than the corresponding angular momentum, electric charge, and magnetic charge of the test particle. In Part II of this dissertation possible black hole interior solutions are studied. The Cauchy horizons and locally naked timelike singularities of the charged (and/or rotating) solutions are contrasted with the spacelike all-encompassing singularity of the Schwarzschild solution. It is determined which portions of the analytic extension of the Reissner-Nordstroem solution are relevant to realistic gravitational collapse
Are Black Holes Elementary Particles?
Ha, Yuan K.
2009-01-01
Quantum black holes are the smallest and heaviest conceivable elementary particles. They have a microscopic size but a macroscopic mass. Several fundamental types have been constructed with some remarkable properties. Quantum black holes in the neighborhood of the Galaxy could resolve the paradox of ultra-high energy cosmic rays detected in Earth's atmosphere. They may also play a role as dark matter in cosmology.
International Nuclear Information System (INIS)
Camenzind, M.
2005-01-01
While physicists have been grappling with the theory of black holes (BH), as shown by the many contributions to the Einstein year, astronomers have been successfully searching for real black holes in the Universe. Black hole astrophysics began in the 1960s with the discovery of quasars and other active galactic nuclei (AGN) in distant galaxies. Already in the 1960s it became clear that the most natural explanation for the quasar activity is the release of gravitational energy through accretion of gas onto supermassive black holes. The remnants of this activity have now been found in the centers of about 50 nearby galaxies. BH astrophysics received a new twist in the 1970s with the discovery of the X-ray binary (XRB) Cygnus X-1. The X-ray emitting compact object was too massive to be explained by a neutron star. Today, about 20 excellent BH candidates are known in XRBs. On the extragalactic scale, more than 100.000 quasars have been found in large galaxy surveys. At the redshift of the most distant ones, the Universe was younger than one billion year. The most enigmatic black hole candidates identified in the last years are the compact objects behind the Gamma-Ray Bursters. The formation of all these types of black holes is accompanied by extensive emission of gravitational waves. The detection of these strong gravity events is one of the biggest challenges for physicists in the near future. (author)
Stationary black holes as holographs
Energy Technology Data Exchange (ETDEWEB)
Racz, Istvan [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-01 (Japan); MTA KFKI, Reszecske- es Magfizikai Kutatointezet, H-1121 Budapest, Konkoly Thege Miklos ut 29-33 (Hungary)
2007-11-21
Smooth spacetimes possessing a (global) one-parameter group of isometries and an associated Killing horizon in Einstein's theory of gravity are investigated. No assumption concerning the asymptotic structure is made; thereby, the selected spacetimes may be considered as generic distorted stationary black holes. First, spacetimes of arbitrary dimension, n {>=} 3, with matter satisfying the dominant energy condition and allowing a non-zero cosmological constant are investigated. In this part, complete characterization of the topology of the event horizon of 'distorted' black holes is given. It is shown that the topology of the event horizon of 'distorted' black holes is allowed to possess a much larger variety than that of the isolated black hole configurations. In the second part, four-dimensional (non-degenerate) electrovac distorted black hole spacetimes are considered. It is shown that the spacetime geometry and the electromagnetic field are uniquely determined in the black hole region once the geometry of the bifurcation surface and one of the electromagnetic potentials are specified there. Conditions guaranteeing the same type of determinacy, in a neighbourhood of the event horizon, on the domain of outer communication side are also investigated. In particular, they are shown to be satisfied in the analytic case.
Atomic structure in black hole
International Nuclear Information System (INIS)
Nagatani, Yukinori
2006-01-01
We propose that any black hole has atomic structure in its inside and has no horizon as a model of black holes. Our proposal is founded on a mean field approximation of gravity. The structure of our model consists of a (charged) singularity at the center and quantum fluctuations of fields around the singularity, namely, it is quite similar to that of atoms. Any properties of black holes, e.g. entropy, can be explained by the model. The model naturally quantizes black holes. In particular, we find the minimum black hole, whose structure is similar to that of the hydrogen atom and whose Schwarzschild radius is approximately 1.1287 times the Planck length. Our approach is conceptually similar to Bohr's model of the atomic structure, and the concept of the minimum Schwarzschild radius is similar to that of the Bohr radius. The model predicts that black holes carry baryon number, and the baryon number is rapidly violated. This baryon number violation can be used as verification of the model. (author)
Miller, M. Coleman; Colbert, E. J. M.
2004-01-01
The mathematical simplicity of black holes, combined with their links to some of the most energetic events in the universe, means that black holes are key objects for fundamental physics and astrophysics. Until recently, it was generally believed that black holes in nature appear in two broad mass ranges: stellar-mass (M~3 20 M⊙), which are produced by the core collapse of massive stars, and supermassive (M~106 1010 M⊙), which are found in the centers of galaxies and are produced by a still uncertain combination of processes. In the last few years, however, evidence has accumulated for an intermediate-mass class of black holes, with M~102 104 M⊙. If such objects exist they have important implications for the dynamics of stellar clusters, the formation of supermassive black holes, and the production and detection of gravitational waves. We review the evidence for intermediate-mass black holes and discuss future observational and theoretical work that will help clarify numerous outstanding questions about these objects.
Regular black hole in three dimensions
Myung, Yun Soo; Yoon, Myungseok
2008-01-01
We find a new black hole in three dimensional anti-de Sitter space by introducing an anisotropic perfect fluid inspired by the noncommutative black hole. This is a regular black hole with two horizons. We compare thermodynamics of this black hole with that of non-rotating BTZ black hole. The first-law of thermodynamics is not compatible with the Bekenstein-Hawking entropy.
Black holes, qubits and octonions
International Nuclear Information System (INIS)
Borsten, L.; Dahanayake, D.; Duff, M.J.; Ebrahim, H.; Rubens, W.
2009-01-01
We review the recently established relationships between black hole entropy in string theory and the quantum entanglement of qubits and qutrits in quantum information theory. The first example is provided by the measure of the tripartite entanglement of three qubits (Alice, Bob and Charlie), known as the 3-tangle, and the entropy of the 8-charge STU black hole of N=2 supergravity, both of which are given by the [SL(2)] 3 invariant hyperdeterminant, a quantity first introduced by Cayley in 1845. Moreover the classification of three-qubit entanglements is related to the classification of N=2 supersymmetric STU black holes. There are further relationships between the attractor mechanism and local distillation protocols and between supersymmetry and the suppression of bit flip errors. At the microscopic level, the black holes are described by intersecting D3-branes whose wrapping around the six compact dimensions T 6 provides the string-theoretic interpretation of the charges and we associate the three-qubit basis vectors, |ABC>(A,B,C=0 or 1), with the corresponding 8 wrapping cycles. The black hole/qubit correspondence extends to the 56 charge N=8 black holes and the tripartite entanglement of seven qubits where the measure is provided by Cartan's E 7 contains [SL(2)] 7 invariant. The qubits are naturally described by the seven vertices ABCDEFG of the Fano plane, which provides the multiplication table of the seven imaginary octonions, reflecting the fact that E 7 has a natural structure of an O-graded algebra. This in turn provides a novel imaginary octonionic interpretation of the 56=7x8 charges of N=8: the 24=3x8 NS-NS charges correspond to the three imaginary quaternions and the 32=4x8 R-R to the four complementary imaginary octonions. We contrast this approach with that based on Jordan algebras and the Freudenthal triple system. N=8 black holes (or black strings) in five dimensions are also related to the bipartite entanglement of three qutrits (3-state systems
Energy Technology Data Exchange (ETDEWEB)
Corda, Christian [Institute for Theoretical Physics and Advanced Mathematics (IFM) Einstein-Galilei, Prato (Italy); Istituto Universitario di Ricerca ' ' Santa Rita' ' , Prato (Italy); International Institute for Applicable Mathematics and Information Sciences (IIAMIS), Hyderabad (India)
2013-12-15
Introducing a black hole (BH) effective temperature, which takes into account both the non-strictly thermal character of Hawking radiation and the countable behavior of emissions of subsequent Hawking quanta, we recently re-analysed BH quasi-normal modes (QNMs) and interpreted them naturally in terms of quantum levels. In this work we improve such an analysis removing some approximations that have been implicitly used in our previous works and obtaining the corrected expressions for the formulas of the horizon's area quantization and the number of quanta of area and hence also for Bekenstein-Hawking entropy, its subleading corrections and the number of micro-states, i.e. quantities which are fundamental to realize the underlying quantum gravity theory, like functions of the QNMs quantum ''overtone'' number n and, in turn, of the BH quantum excited level. An approximation concerning the maximum value of n is also corrected. On the other hand, our previous results were strictly corrected only for scalar and gravitational perturbations. Here we show that the discussion holds also for vector perturbations. The analysis is totally consistent with the general conviction that BHs result in highly excited states representing both the ''hydrogen atom'' and the ''quasi-thermal emission'' in quantum gravity. Our BH model is somewhat similar to the semi-classical Bohr's model of the structure of a hydrogen atom. The thermal approximation of previous results in the literature is consistent with the results in this paper. In principle, such results could also have important implications for the BH information paradox. (orig.)
Corda, Christian
2013-12-01
Introducing a black hole (BH) effective temperature, which takes into account both the non-strictly thermal character of Hawking radiation and the countable behavior of emissions of subsequent Hawking quanta, we recently re-analysed BH quasi-normal modes (QNMs) and interpreted them naturally in terms of quantum levels. In this work we improve such an analysis removing some approximations that have been implicitly used in our previous works and obtaining the corrected expressions for the formulas of the horizon's area quantization and the number of quanta of area and hence also for Bekenstein-Hawking entropy, its subleading corrections and the number of micro-states, i.e. quantities which are fundamental to realize the underlying quantum gravity theory, like functions of the QNMs quantum "overtone" number n and, in turn, of the BH quantum excited level. An approximation concerning the maximum value of n is also corrected. On the other hand, our previous results were strictly corrected only for scalar and gravitational perturbations. Here we show that the discussion holds also for vector perturbations. The analysis is totally consistent with the general conviction that BHs result in highly excited states representing both the "hydrogen atom" and the "quasi-thermal emission" in quantum gravity. Our BH model is somewhat similar to the semi-classical Bohr's model of the structure of a hydrogen atom. The thermal approximation of previous results in the literature is consistent with the results in this paper. In principle, such results could also have important implications for the BH information paradox.
Black holes: the membrane paradigm
International Nuclear Information System (INIS)
Thorne, K.S.; Price, R.H.; Macdonald, D.A.
1986-01-01
The physics of black holes is explored in terms of a membrane paradigm which treats the event horizon as a two-dimensional membrane embedded in three-dimensional space. A 3+1 formalism is used to split Schwarzschild space-time and the laws of physics outside a nonrotating hole, which permits treatment of the atmosphere in terms of the physical properties of thin slices. The model is applied to perturbed slowly or rapidly rotating and nonrotating holes, and to quantify the electric and magnetic fields and eddy currents passing through a membrane surface which represents a stretched horizon. Features of tidal gravitational fields in the vicinity of the horizon, quasars and active galalctic nuclei, the alignment of jets perpendicular to accretion disks, and the effects of black holes at the center of ellipsoidal star clusters are investigated. Attention is also given to a black hole in a binary system and the interactions of black holes with matter that is either near or very far from the event horizon. Finally, a statistical mechanics treatment is used to derive a second law of thermodynamics for a perfectly thermal atmosphere of a black hole
Cosmology with primordial black holes
International Nuclear Information System (INIS)
Lindley, D.
1981-09-01
Cosmologies containing a substantial amount of matter in the form of evaporating primordial black holes are investigated. A review of constraints on the numbers of such black holes, including an analysis of a new limit found by looking at the destruction of deuterium by high energy photons, shows that there must be a negligible population of small black holes from the era of cosmological nucleosynthesis onwards, but that there are no strong constraints before this time. The major part of the work is based on the construction of detailed, self-consistent cosmological models in which black holes are continually forming and evaporating The interest in these models centres on the question of baryon generation, which occurs via the asymmetric decay of a new type of particle which appears as a consequence of the recently developed Grand Unified Theories of elementary particles. Unfortunately, there is so much uncertainty in the models that firm conclusions are difficult to reach; however, it seems feasible in principle that primordial black holes could be responsible for a significant part of the present matter density of the Universe. (author)
Black holes: a slanted overview
International Nuclear Information System (INIS)
Vishveshwara, C.V.
1988-01-01
The black hole saga spanning some seventy years may be broadly divided into four phases, namely, (a) the dark ages when little was known about black holes even though they had come into existence quite early through the Schwarzschild solution, (b) the age of enlightenment bringing in deep and prolific discoveries, (c) the age of fantasy that cast black holes in all sorts of extraordinary roles, and (d) the golden age of relativistic astrophysics - to some extent similar to Dirac's characterisation of the development of quantum theory - in which black holes have been extensively used to elucidate a number of astrophysical phenomena. It is impossible to give here even the briefest outline of the major developments in this vast area. We shall only attempt to present a few aspects of black hole physics which have been actively pursued in the recent past. Some details are given in the case of those topics that have not found their way into text books or review articles. (author)
Black women in menopausal transition.
Im, Eun-Ok; Lee, Seung Hee; Chee, Wonshik
2010-01-01
To describe the experience of menopausal symptoms of midlife Black women in the United States. Qualitative online forum using a feminist perspective. Internet communities for midlife women and Blacks. Twenty midlife Black women recruited using a quota sampling method. A 6-month online forum was conducted with seven discussion topics on menopausal symptoms. The discussion topics were posted sequentially on the forum site, and the women posted messages at their convenience over 6 months. The data were analyzed using thematic analysis. The identified themes were raised to be strong, accepting a natural aging process, silent and without knowledge, and our own experience. The women tried to be strong during their menopausal transitions while dealing with other important family matters. The women did not report their menopausal symptoms and were silent about or downplayed their symptoms, but many emphasized the importance of education about menopausal symptoms and highlighted their own lack of knowledge. These women generally did not talk about their symptoms because they believed that nobody except other Black midlife women could understand their menopausal experience. Health care providers need to develop a mechanism to deliver the necessary knowledge about menopausal symptoms and management strategies to Black midlife women in their health care practices.
Time dependent black holes and scalar hair
International Nuclear Information System (INIS)
Chadburn, Sarah; Gregory, Ruth
2014-01-01
We show how to correctly account for scalar accretion onto black holes in scalar field models of dark energy by a consistent expansion in terms of a slow roll parameter. At leading order, we find an analytic solution for the scalar field within our Hubble volume, which is regular on both black hole and cosmological event horizons, and compute the back reaction of the scalar on the black hole, calculating the resulting expansion of the black hole. Our results are independent of the relative size of black hole and cosmological event horizons. We comment on the implications for more general black hole accretion, and the no hair theorems. (paper)